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Subject: comp.periphs.scsi FAQ part 1 of 2

This article was archived around: 01 Apr 1998 17:53:29 GMT

All FAQs in Directory: scsi-faq
All FAQs posted in: comp.periphs.scsi
Source: Usenet Version

Archive-name: scsi-faq/part1 Posting-Frequency: monthly Last-modified: 1998/3/31
Note: The FAQ has undergone a facelift. The source file is now a Microsoft Word for Windows (Office '97) document so that it is be possible to generate both a text and an HTML version from the same document. I'm not thrilled with the text file that I'm getting out of Microsoft Word, but I believe all the information is there. The HTML version will make it much easier and faster to look up information by providing hyperlinks. The text version will continue to be produced until there is no significant interest in it. If you would be unable to read an HTML version of the FAQ and want to make sure I continue to produce the plain text version, email me at: gfield@zk3.dec.com explaining why. So far I have only received one request for the text version, so it may not live much longer. Gary Field ----------------------------------------------------------------------- SCSI FAQ Frequently Asked Questions List for comp.periphs.scsi Current Editor: Gary Field (gfield@zk3.dec.com) (Where you see reference to [Editor(GF)] that means me.) Last updated: March 31, 1998 Skip to Table of Contents FAQ history: Created by Johnathan Vail (vail@prepress.pps.com) from articles submitted to him by comp.periph.scsi readers. Maintained by Johnathan Vail until November 1993. Where to get the latest copy of this FAQ: The comp.periphs.scsi FAQ is posted to Usenet during the first week of each month. As of February 1998 it is available in both a text file version and an HTML version. Some sites may not yet be archiving the HTML version. A recent version can be obtained via anonymous ftp from: ftp.ultranet.com: pub/gfield/scsi/scsifaq.txt and scsifaq.html Note: the gfield directory will not show up using DIR, but it's actually there. Just CD to it. OR rtfm.mit.edu: pub/usenet-by-group/comp.periphs.scsi/comp.periphs.scsi_FAQ_part_* via World Wide Web (WWW): http://www.cis.ohio-state.edu/hypertext/faq/usenet/scsi-faq/ OR http://www.ultranet.com/~gfield/gary/scsi.html OR http://fieldnet.ne.mediaone.net/gary/scsi.html Attention SCSI vendors: There are a few articles in this FAQ where vendor contact information, and in a few cases, part numbers, are listed. This is not an attempt to steer business to any particular vendor but only to provide possible sources of certain "hard to find" SCSI accessories (particularly special cables, adapters and terminators). If you want to be listed in one or more articles please send your contact info and which items you can provide to the FAQ editor. I will not include pointers for devices like hard disks, tapes, CDROMs etc., which I consider readily available. Table of Contents: Categories: Generic SCSI Questions SCSI Documentation and Books SCSI Manufacturer Contact Information Manufacturer Specific Questions Platform Specific Questions Device Model Specific Questions Host Adapter Model Specific Questions Generic SCSI Questions: What is SCSI? What information should I provide when asking a question in the comp.periphs.scsi newsgroup? What do all these SCSI buzzwords mean? What is the history of SCSI (What is SASI)? Can I access a SASI drive with a SCSI controller? How should I lay out my SCSI bus? What should I avoid? Where do I put the terminators? What is a SCSI terminator? Why do I need them? Where Should I place the SCSI adapter on the SCSI bus? Is the spacing of connectors on a SCSI cable important? How long can my SCSI bus be? What are the pros and cons regarding SCSI vs IDE/ATA ? Should I spend the extra money on SCSI or just get IDE? Can I have both IDE/ATA drives and SCSI in the same system? Is it possible for two computers to access the same SCSI disks? Is it possible for two computers to access the same SCSI tape? What is FAST SCSI ? How can I check a passive SCSI terminator ? Can someone explain to me the difference between 'normal' SCSI and differential SCSI? What are the pinouts for differential SCSI? How can I tell if I have a single ended or differential drive ? What are the pinouts for SCSI connectors? I've got a SCSI disk with an 80 pin connector. Someone called it an SCA drive. Can I connect this to my SCSI bus? What is the difference between SCSI-1 and SCSI-2? What is the difference between SCSI-2 and SCSI-3? Are SCSI-3 hard drives and/or controllers available yet? After perusing the latest issue of Computer Shopper, I came away with the impression that companies are calling F&W SCSI-2 HD's SCSI-3. Is this an incorrect assumption, or is F&W SCSI-2 known as SCSI-3? Is SYNCHRONOUS faster than ASYNCHRONOUS? Is the NCR 53C90 Faster than spec? What is ASPI? What is CAM? What is FPT (Termination)? What is Active Termination? Why Is Active Termination Better? How can I tell whether an unmarked terminator is active or passive? Where can I buy terminators ? What is Plug and Play SCSI? Will attaching a SCSI-1 device to my SCSI-2 bus hurt its performance? Can I connect a SCSI-3 disk to my SCSI-1 host adapter? Can I connect a SCSI-2 CDROM to a SCSI-3 host adapter? Can I connect a Narrow SCSI2 disk to a WIDE SCSI3 host adapter? Can I connect a WIDE device to my narrow SCSI host adapter? Can I connect a narrow device to my WIDE SCSI host adapter? How does device ID numbering work with WIDE vs NARROW devices? What is spindle-sync and why would I want it? What if I have a SCSI drive larger than a gigabyte (1024MB)? My SCSI bus works, but is not reliable. What should I look at? Where can I find information about programming using the ASPI interface from DOS and Windows? What kinds of Optical Drives are available? I connected an old narrow device to my WIDE bus with a 68 pin to 50 pin adapter. Now my TERMPWR seems to be shorted out. What is happening? Table of Contents SCSI Documentation and Books: Where can I get various SCSI documentation? How can I find out about the emerging SCSI standards? Where can I get official ANSI SCSI documents? What SCSI books and tutorials are available? Where can I find SCSI info on the Web? Where can I get information on various disk drives and controllers? Table of Contents SCSI Manufacturer Contact Information: How can I contact: Adaptec Archive Corporation (see Seagate) BusLogic /Bustek / Mylex Corel Future Domain Fujitsu Quantum Seagate Conner Peripherals Maxtor NCR Philips Symbios Logic UltraStor Tecmar Technologies (formerly Wangtek, WangDAT, Sytron, and Rexon) Western Digital DPT (Distributed Processing Technology) Micropolis Legacy Storage System Table of Contents Manufacturer Specific Questions: Where can I get SCSICNTL.EXE and other Adaptec files? Where can I get technical information and jumper settings for HP drives ? Who manufactures SCSI extenders and Single-Ended to Differential converters ? Table of Contents Platform Specific Questions: What are the general steps I need to do to install a SCSI disk to be used with Windows? My SCSI CDROM only works when Windows 95 is installed. How can I get Windows 95 installed? Is this a catch 22? Are there any storage related reasons to upgrade to Windows 95 OSR2? Under Windows 95 OSR2 I can only see the first 8 GB of my 9 GB disk. Whatís going on? I'm having problems with my Adaptec 2940xx under Windows 95 but it works OK under other O/Ses (like Linux or Windows NT). Table of Contents Device Model Specific Questions: What are the jumpers on my Conner drive? What are the jumpers for my Wangtek 5150 drive? How do I configure my HP DDS DAT tape drive? Table of Contents Host Adapter Model Specific Questions: What is the problem with the Adaptec 1542C and external cables? What is the difference between the Adaptec 1542A and 1542B? What are the differences between the Adaptec 1542B and the 1542C? What are the differences between the 1542C and the 1542CF? Where can I get drivers (ASPI and other) for the WD7000 FASST2 host adapter? How to replace Macintosh internal HD and terminate the SCSI chain properly? I changed the host adapter in my system and now my disk doesnít work. Why? Table of Contents End Answers to the Questions: ==== QUESTION: What is SCSI? ANSWER From: LSD, L.J.Sak@Kub. Edited by Gary Field(gfield@zk3.dec.com) ==== SCSI stands for Small Computer Systems Interface. It's a standard for connecting peripherals to your computer via a standard hardware interface, which uses standard SCSI commands. The SCSI standard can be divided into SCSI (SCSI1) and SCSI2 (SCSI wide and SCSI wide and fast). SCSI2 is the most recent version of the SCSI command specification and allows for scanners, hard disk drives, CD-ROM players, tapes [and many other devices] to connect. Table of Contents ==== Question: What information should I provide when asking a question in the comp.periphs.scsi newsgroup? Answer From: Gary Field(gfield@zk3.dec.com) ==== In order for most SCSI problems to be resolved, one needs to provide at least the following: Type of system (PC, SPARC or Alpha Workstation, etc.) If PC, what type of motherboard? Operating System (DOS, Windows 3.x, Win 95/98, Win NT 4/5, Linux, other UNIX) Specific SCSI host adapter (Symbios xxxx, Adaptec xxxx, etc) List of attached devices (and for disks, whether they're WIDE or NARROW) Length of SCSI bus Where the terminators are located Whether the configuration is new, or was working before. It may seem like a lot of information to provide, but unless you have some SCSI experience, you may not realize how many factors can affect whether the system works properly or not. If you don't know what some of these things mean, read the rest of this document until you do. You'll get much more help if you appear to have made an effort to find the answer on your own before asking for help. Asking a question like "My scanner doesn't work, how come?" may not even get you a response. Table of Contents ==== Question: What do all these SCSI buzzwords mean? Answer From: hennes@stack.urc.tue.nl (Hennes Passmann)[Editor(GF)] ==== -Host adapter: The card that connects your computer to the SCSI-bus. Usually called SCSI-controller by marketing droids. -Terminators (passive): A group of resistors on the physical ends of a single ended SCSI-bus (and only on these ends) that dampens reflected signals from the ends of the bus. Each terminated signal is connected by: * 220 Ohm to +5 volt (TERMPWR) * 330 Ohm to ground. The 18 signals that are terminated are: I/O, Req, C/D, Sel, Msg, Rst, Ack, Bsy, Atn, DB(p), DB(7) ... DB(0). -Terminators (active). Rather than passive terminators that use TERMPWR which may not be exactly +5v, active terminators use a voltage regulator. -Single ended: "Normal" electrical signals. Uses open collector to the SCSI bus, [usually] survives wrong cable insertion. DIFFSENSE signal is used to detect connection of wrong type devices. The max. length for SCSI-1 is a 6 meter cable with stubs of max 10cm allowed to connect a device to the main-cable. Most devices are single ended. -Differential: Uses two wires to drive one signal. Max. cable length of 25 meters. Electrically incompatible with single ended devices! SCSI-1 and upwards. -Apple kludge: The single ended 50 pins cable has been reduced to 25 pins by tying most grounds together. DB25 connector (like a parallel port). Often used as the external SCSI connector. -Asynchronyous SCSI: A way of sending data over the SCSI-bus. The initiator sends a command or data over the bus and then waits until it receives a reply (e.g. an ACKnowledge). All commands are send asynchronously over the 8 bit part of the SCSI-bus. -Synchronous SCSI. Rather then waiting for an ACK, devices that both support synchronous SCSI can send multiple bytes over the bus in the folowing way: send data1 : send data2 : ... : send data3 (max outstanding bytes) : wait : wait : response1 : reponse2: ... This improves throughput, especially if you use long cables. (The time that a signal travels from one end of the cable to the other end of the cable IS relevant.) -Fast SCSI: Fast SCSI allows faster timing on the bus. ( 10MHz instead of 5MHz ) On a 8 bit SCSI-bus this increases the *theoretical* maximum speed from 5MB/s to 10MB/s. I know of no single drive that reaches these speeds. - RAID:[Added by Editor(GF) Corrected by Fredrik Bjork (ace@varberg.se)] A Redundant Array of Independant Disks is a set of drives connected to a special dual ported SCSI adapter that allows certain types of access optimization. A RAID 0 array stripes the data accross multiple drives to decrease data latency. A RAID 1 array mirrors the data on multiple drives for increased data integrity. A RAID 5 array uses extra drives in a distributed manner to store parity information that can be used to apply data correction and recover any data in the event of any individual disk failure. This provides high reliability. -Ultra SCSI: Allows up to 20MHz signals on the bus. -Wide SCSI: Uses an extra cable (or 68 pin P cable) to send the data 16 or 32 bits wide. This allows for double or quadruple speed over the SCSI- bus. Note that no *single* drive reaches these speeds, but groups of several drives can. Table of Contents === Question: What is the history of SCSI (What is SASI)? Answer From: hennes@stack.urc.tue.nl (Hennes Passmann) ==== #include <stddisclaimer.h> 1979 The disk drive manufacturer Shugart begin working on a new drive interface with logical rather then physical adressing. It used 6 byte commands. Shugart Associates Systems Interface (20 pages long) made public. A few SASI drives are developed 1980 Attempt to make SASI an ANSI standard failed. 1981 Shugart and NCR request an ANSI committee be formed for SASI 1982 ANSI committee X3T9.2 is formed. SCSI adds the ATN signal to the bus and creates the message protocol. 1983 Development of SCSI drives and ST-506 to SCSI bridges begins. 1985 CCS (Common Command Set) used in most disk drives. Only disk and tape commands were adequately specified. 1986 Work begins on SCSI-2. 1986 SCSI-1 becomes official as ANSI X3.131-1986 (yes, after the work had begun on SCSI-2) 6 and 10 byte commands. SCSI-2 specifies CDROM commands. 1988 Production of SCSI-2 devices begins. 1993 Work begins on SCSI-3. 1994 SCSI-2 becomes official as X3.131-1994. SCSI-2 is backwards compatible with SCSI-1 and adds the following: *Fast SCSI-2. Optional bus speed of 10MHz instead of 5MHz. *Wide Optional 16 or 32 bit cable instead of 8 bits. *more commands defined, many optional (I'm not going to type the entire list here) *broader support for non-disk devices (tape.CDROM,Scanners....) SCSI-2 devices can talk to the host adaptor on their own inititive. (e.g. to set in which mode they shoud operate, FAST or not, wide, extra wide or normal ...) This can confuse some older SCSI-1 HA. 1995 Production of drives that have some SCSI-3 enhancements. Ultra SCSI: Bus speed of 20MHz? 1996: SCSI-3 proposals include: -Support for graphical commands. -Fibre channel protocol (fibre channel) -Serial packet protocol (IEEE P1394) -SCSI-3 general packet protocol (almost all serial interfaces) and of course the old SCSI-2 commands and more. -Low Voltage Differential Parallel interface -CD-R command set and algorithms Future(after 1996): SCSI-3 becomes official SCSI becomes a more network-like environment where devices can be physically distributed and shared more easily. Table of Contents === Question: Can I access SASI drive with SCSI controller? Answer From: Gary Field(gfield@zk3.dec.com) ==== Well, the answer is a definite maybe, but very unlikely. Old low performance SCSI adapters and drivers that use only a minimal subset of the SCSI commands may work with SASI devices that happen to support the INQUIRY command. Newer adapters and drivers expect to be able to use messages and will get very upset with a SASI device that doesn't understand them. In reality, there is no practical reason to do this. Any SASI device is so obsolete that is has no real value in a system being used in 1990 or later. Table of Contents ==== Question: How should I lay out my SCSI bus? What should I avoid? Question: Where do I put the terminators? Question: Where should the adapter card be placed? Answers From: Nick Kralevich <nickkral@cory.eecs.berkeley.edu> edited by Gary Field (gfield@zk3.dec.com) ==== One confusing thing about SCSI is what the SCSI bus is supposed to look like, and how devices should be placed on the bus. The SCSI bus MUST run continuously from one device to another, like this: DEVICE A --------- DEVICE B --------- DEVICE C -------- DEVICE D Where device A, B, C, and D can either be internal or external devices. The devices on the SCSI bus should have at least 4 to 6 inches of cable between devices. This is to satisfy the SCSI-2 requirement that "stubs" be placed at least .1 meters apart. Some devices that have a lot of internal wiring between the connector and the SCSI chip can look like a "stub" or bus discontinuity. The reason for all these requirements is that a SCSI bus is really 18 "transmission lines" in the wave theory sense. A pulse propagating along it will "reflect" from any part of the transmission line that is different from the rest of it. These relections add and subtract in odd combinations and cause the original pulse to be distorted and corrupted. The terminators "absorb" the energy from the pulses and prevent relections from the ends of the bus. They do this because they (hopefully) have the same impedance as the rest of the transmission line. The SCSI bus must not have any "Y" shape cabling. For example, setting up a cable that looks like this is NOT allowed: DEVICE B \ \ \ >------------- DEVICE C ----------- DEVICE D / / / DEVICE A Where do I put the terminators? Termination must be present at two and ONLY two positions on the SCSI bus, at the beginning of the SCSI bus, and at the end of the SCSI bus. There MUST be no more than two, and no less than two, terminators on the bus. Termination must occur within 4 inches (.1 meter) of the ends of the SCSI bus. The following ARE acceptable: +------------+----------+-----------+-----------+---------+ | | | | | | DEVICE A Unconnected Unconnected DEVICE B DEVICE C Adapter Terminated Terminated +------------+----------+-----------+-----------+---------+ | | | | | | DEVICE A Unconnected DEVICE B Unconnected Adapter DEVICE C Terminated Terminated +------------+----------+-----------+-----------+---------+ | | | | | | Adapter DEVICE A DEVICE B Unconnected Unconnected DEVICE C Terminated Terminated The following ARE NOT allowed: +------------+----------+-----------+-------------------+ | | | | | DEVICE A DEVICE B Adapter Unconnected Unconnected Terminated Terminated +------------+----------+-----------+-----------+ | | | | | Termination DEVICE A DEVICE B DEVICE C Adapter Terminated Where Should I place the SCSI adapter on the SCSI bus? The placement of the SCSI adapter card can be on the end, at the beginning, or somewhere in the middle of the SCSI bus. Quite frankly, placement of the controller card isn't special. The adapter card is just another device on the SCSI bus. As long as the rules above and in other sections of this FAQ are followed, there should be no problem placing the adapter card anywhere on the SCSI bus. However, if you place the adapter card somewhere in the middle of the SCSI bus, you must be sure to disable termination on the adapter card. As noted previously, a SCSI device is only allowed to have terminations if it's at the end of the bus. Only two terminators are allowed to terminate the SCSI bus, one at each end. One last note: It doesn't make any difference where each SCSI ID is placed along the bus. It only matters that no two devices have the same ID. Don't forget that the adapter has an ID too. (Usually ID 7). Table of Contents === Question: What is a SCSI terminator? Why do I need them? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== A SCSI bus is a transmission line. To prevent reflections from the ends of the bus, you need a device which makes the transmission line appear to be of infinite length. This is done by attaching resistors which have the same resistance as the characteristic impedance of the transmission line to the ends of the bus. Also, since SCSI line drivers are open-collector (which can only pull a signal low), a pull-up resistor is needed to pull the signal high when it's not asserted. If the ends of the bus are not terminated, the signal pulses will reflect off these open ends and travel back along the bus in the other direction. The resulting adding and cancelling of signal amplitudes distorts and destroys the SCSI signals. There are two basic types of terminators, active and passive. Table of Contents === Question: Is the spacing of connectors on a SCSI cable important? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== The ANSI SCSI spec's say that "stubs" on a SCSI bus must not be any more than .1 meters (4 in.) long. In the most recent spec's there are also guidelines that say you shouldn't place "stubs" any closer than .3 meters (12 in.) apart. Since each device attached acts as a "stub", you really shouldn't place connectors any closer than this. This gets to be more important as your bus performance goes up. i.e. with Fast20 it is very important, but with SCSI-1 it doesn't really matter much. Since Fast20 also limits your overall bus length to 1.5 meters (for single ended) this also means you shouldn't really connect more than 5 devices for best reliability. Table of Contents === QUESTION: How long can my SCSI bus be? ANSWER From: Gary Field (gfield@zk3.dec.com) The SCSI length limits are based on the speed of the fastest device attached to the bus. Here's a table which shows the limits: Speed of FASTEST device Max. single-ended bus length Max. HV Diff. bus len. 5 MHz (SCSI1 synch.) 6 meters 25 meters 10 MHz (SCSI2 FAST) 3 meters(not rec.) 25 meters 20 MHz (Ultra or Fast20) 1.5 meters(not rec.) ? 40 MHz (Ultra2 or Fast40) Only differential connections allowed These limits assume the use of good quality cable which maintains its characteristic impedance between 90 and 130 Ohms and the use of active terminators at each end of the bus. Notice that I used the term MHz to specify speed since MB/sec. changes with the bus width. When Low Voltage Differential(LVD) devices are available, this will allow lengths between the single-ended numbers and the HV Diff. numbers. Note: Bus width doesn't change the maximum allowable length. The bus width is independent of bus length or speed. The above table assumes that you know the max. speed of your devices (usually by looking in the manuals). Some software (like Adaptec EZ- SCSI) provides a driver status monitor which will tell you what mode the devices are actually in. This is important since any synchronous speed must be negotiated by either the device or the adapter. The speed actually used will be the least common denominator between the two. For example, if a Fast20 disk is attached to a 'SCSI2" host adapter that only goes up to Fast10, the device will only run at 10 MHz. Table of Contents ==== QUESTION: What are the pros and cons regarding SCSI vs IDE/ATA ? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== Pros of IDE/ATA: Inexpensive due to high volume of production Supported directly by system BIOS in most cases Less overhead per command Cons of IDE/ATA: Very limited device attachment (two drives including CDROMs) Only supports disk, CDROM (and limited support for tape) Single threaded (commands do not overlap even with a second drive) CPU is tied up transferring all data IDE/ATA and ATAPI evolved as one kludge on top of another (so compatibility is not always good) Cannot handle scatter/gather operations well Pros of SCSI: Flexible device attachment (up to 7 or 15 devices per SCSI bus) Support for almost any peripheral type (disk, tape, CDROM, scanner etc) All commands can overlap with commands on other devices Usually uses DMA to transfer data (which frees CPU for other tasks) Interface and protocol is carefully specified by ANSI. Largest, highest performance devices are available in SCSI before IDE Most adapters can do scatter/gather DMA which is a necessity in virtual memory systems (Like Unix, NT) (Win 95 ?) Cons of SCSI: Generally more expensive than IDE/ATA Slightly more complicated to install than IDE/ATA --------------- Now that I've said that, here's an article to show that there's more than one opinion on this subject: From: Ed Schernau <mithrandir@ids.net> Subject: FYI: EIDE and DMA/Scatter-Gather The Western Digital Caviar EIDE drive that came in what is now the file server in our office came with a Win3.x 32 BDA driver which allowed the user to select DMA type (B or F) and to implement scatter-gather. Also, the Intel Triton chipset implements 2 EIDE controllers, and I know that at least the 1 on the PCI bus supports bus-mastering, as well as DMA. However, PIO transfers can be faster, the infamous Mode 4 can in theory, do 16.6 MB/sec and I've heard of a Mode 5 which can do 22 MB/sec. Which [PIO] is only a benefit in single-tasking systems like DOS or Win3.x. Sounds like Intel is trying to make EIDE into SCSI, eh? Table of Contents ==== Should I spend the extra money on SCSI or just get IDE? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== For home users this is a difficult question to answer in general. It totally depends on how you use your system, what operating system is installed, and whether you will add more I/O devices in the future. For server systems in a corporate environment the only sensible answer is to go with SCSI peripherals. IDE/EIDE is single threaded by nature. The current command must complete before additional commands can start. With most IDE adapters the processor must be involved in reading/writing the data from/to memory. Another drawback is that only two drives can be attached. In a single drive single-tasking system IDE will probably be slightly faster and is definitely less expensive. When you start talking about multi-tasking operating systems (like Win95, WinNT, Unix, OS/2 and Netware) SCSI is now a big advantage. As disk drives get bigger, backup devices are becoming even more important. In my opinion floppy tapes just aren't satisfactory. They're too slow, too unreliable, non-portable(media exchange wise not physically), and have low storage capacities. SCSI tape drives are more expensive, but have none of these problems. SCSI devices share the bus bandwidth efficiently by allowing one device to transfer data while another is seeking or rewinding its media. Early SCSI implimentations had some compatibility problems but these days SCSI is simpler to install than EIDE. Each user needs to make this choice individually, but if you don't consider all the issues, you can find yourself needing to re-vamp all your I/O to add a device later on. Before you decide to go with IDE, ask yourself if you will ever want to add a CDROM, CD-R, scanner, or tape drive or need more than two hard disk drives. Here's a discussion that shows some of the advantages of SCSI in more detail: from: Greg Smith (GREGS@lss-chq.mhs.compuserve.com) Under DOS (and DOS/win3.1), there is very little useful work the host can do while waiting for a disk operation to complete. So handing off some work from a 66 MHz 486 to, say, an 8 MHz Z80 (on the controller) does result in a performance loss. Under EVERY other OS worth discussing (Unix, Netware, NT, OS/2, Win95 etc) the processor can go off and do something else while the access is in progress, so the work done by the other CPU can result in a performance increase. In such systems, due to virtual memory, a 64K byte 'contiguous' read requested by a process may be spread to 16 separate physical pages. A good SCSI controller, given a single request, can perform this 'scatter/gather' operation autonomously. ATA requires significant interrupt service overhead from the host to handle this. Another big issue: ATA does not allow more than one I/O request to be outstanding on a single cable, even to different drives. SCSI allows multiple I/O requests to be outstanding, and they may be completed out of order. For instance, process 'A' needs to read a block. The request is sent to the drive, the disk head starts to move, and process 'A' blocks waiting for it. Then, process 'B' is allowed to run; it aslo reads a block from the disk. Process B's block may be sitting in a RAM cache on the SCSI controller, or on the drive itself. Or the block may be closer to the head than process A's block, or on a different drive on the same cable. SCSI allows process B's request to be completed ahead of process A's, which means that process B can be running sooner, so that the most expensive chip - the system CPU - tends to spend less time twiddling its thumbs. Under ATA, the process B request cannot even be sent to the drive until the process A request is complete. These SCSI capabilities are very valuable in a true multi-tasking environment, especialy important in a busy file server, and useless under DOS, which cannot take advantage of them. I tend to hear from people, 'Well, I never use multitasking' because they never actively run two programs at once Ė all but one are 'just sitting there'. Consider what happens though, when you minimize a window which uncovers parts of four other application windows. Each of those applications is sent a message telling it to update part of its window; under win95, they will all run concurrently to perform the update. If they need to access disk (usually because of virtual memory) the smoothness of the update can depend a lot on the disk system's ability to respond to multiple independent read requests and finish them all as quickly as possible; SCSI is better at this. So, yes, ATA is faster under DOS; but SCSI provides advantages which are inaccessible to DOS. They will benefit Win95 however. The cost of intelligent, fast SCSI controllers and drives should decrease as people discover these advantages and start buying them. I should add that many of SCSI's advantages are NOT available with some of the simpler SCSI controllers which were targeted only to the DOS market or part of cheap CDROM add-on kits. Furthermore, SCSI allows far greater flexibility of interconnect. I concede that for the mass market, which likes to buy pre-configured machines, this is but a small advantage. Table of Contents ==== QUESTION: Can I have both IDE/ATA drives and SCSI in the same system? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== The short answer is YES. There are a few issues to consider however. The main issue is which device will be used for booting the system. Under MSDOS, The system BIOS determined this completely. A couple third party BIOSes (like MRBIOS) allowed the user to choose the boot source, but most conventional BIOSes just booted from the IDE if it was present. If no IDE was present then the standard option card BIOS scan would find the SCSI card's BIOS and use it to boot. Under Windows 95 and Windows NT, there are more options. Since the motherboard BIOS is used to load the boot sector that will still happen according to the same rules as under MSDOS described above. After the boot sector is loaded, the O/S's device drivers take over and those can be unloaded or drive letters re-ordered via the O/S configuration tools. Table of Contents ==== QUESTION: Is it possible for two computers to access the same SCSI disks? ANSWER From: burke@seachg.uucp (Michael Burke) ==== Yes, two (or more) systems can be on the same SCSI bus as SCSI disk and tape drives. As long as the SCSI requirements are met - cable lengths, termination and type - the devices can share the SCSI bus. [Editor(GF): Each host adapter needs to have a unique ID just as the devices do. Some adapters don't let you set this. ] The question should be - Are there any O/S' that will allow the sharing of file systems? It would not make sense for two hosts to go about treating shared disks as if they each owned the device. Data would be destroyed pretty quickly. [Editor(GF): CDROM drives can be shared pretty easily because they are by definition READ-ONLY] Disks can be best shared by having two (or more) partitions on a disk. Each host "owning" its own file system. [Editor(GF): You also need to watch out for host adapters that reset the bus when booting. Some adapters let you control this. ] [ Additional editorial comment Editor(GF): The above discussion refers primarily to PCs. There are high end systems that do allow sharing SCSI devices. Usually, this is to allow fault tolerance. Two systems are connected to the same set of SCSI storage devices and when one of them fails, the other takes control. AIX with HACMP, Digital UNIX, and Digital VMS are examples of systems that allow this. - Thanks to Cees de Groot for suggesting this addition.] Table of Contents ==== QUESTION: Is it possible for two computers to access the same SCSI tape? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== Yes, this is not usually as problematic as sharing disks as long as the operator is sensible about what is attempted. Some things you need to watch out for: Both host's device drivers must use RESERVE/RELEASE commands to lock access. This locks the drive for access by only one system, the conflicting host gets BUSY status until the currently accessing host sends a RELEASE cmd. The adapter on both hosts have unique IDs. Good and common grounding of both systems and the devices. SCSI length limits are not violated. Make sure both hosts select the same data transfer mode (synch or asynch). Both hosts can be told which disks and other devices to access and not to attempt to access the ones owned by the other host. Neither host adapter resets the SCSI bus. Table of Contents ==== QUESTION: What is the problem with the Adaptec 1542C and external cables? ANSWER From: Scot Stelter, Adaptec (Product Manager for the AHA-1540) ==== Several articles lately have cited the importance of SCSI-2-compliant cables when cabling SCSI bus subsystems. Perhaps the most accurate and technically detailed one was published in Computer Technology Review in March Ď93 (Volume XIII, No. 3. PP. 6). In short, it explains the double-clocking mechanism that can occur due to cables whose impedance falls below the 90-Ohm SCSI-2 spec. Steep edge speeds on the REQ and ACK lines of the SCSI bus exacerbate the problem, but non-compliant cables are the root cause. Both LAN TIMES in the US (5/24/93, page 115) and CT Magazine in Germany (7/93, page 18) cite this cable problem. In an extensive survey of cables available in the US and Europe, we found that more than half of the cables available have single-ended impedances in the 65 to 80 Ohm range -- below the 90 to 132 Ohms specified in the SCSI-2 spec. It seems that some (not all) cable vendors do not understand the specification, describing their cables as SCSI-2 compliant when they are not. A common misconception is that SCSI-2 means a high-density connector. In fact, there are several connector options. I have published a technical bulletin that summarizes the critical requirements (TB 001, April 1993). An artifact of its faster design left the AHA-1540C with faster edge- speeds than its predecessor, the AHA-1540B. As I have said, this can exacerbate the effect of bad cables. This explains why some users could get their AHA-1540B to work when an early AHA-1540C might not. Essentially, the 1540B was more forgiving than the early 1540Cs. Good cables fixed the problem, but unfortunately for the user, good cables are hard to find. After surveying the cable market and many of our customers, we decided that bad cables were going to be here for a while, and we had to make the 1540C as forgiving as the 1540B was. At the end of April '93 we made a change to the AHA-1540C that involved using a passive filter to reduce the slew rate of the ACK line, the signal that the host adapter drives during normal data transfers. Extensive testing with many intentionally illegal configurations confirms that we succeeded. Prior to release, we tested the AHA-1540C with over 200 peripherals, systems and demanding software programs with no failures. Then, a second team retested the AHA-1540C across a wild combination of temperatures, humidities and other stresses. This testing gives me confidence that the AHA-1540 line continues to serve as the gold standard for SCSI compatibility. Table of Contents ==== QUESTION: What is the difference between the Adaptec 1542A and 1542B? ANSWER From: fishman@panix.com (Harvey Fishman) ==== The AHA-1542A is obsolete and no longer supported by Adaptec. They stopped providing firmware upgrades at some level prior to the equivalence to the 3.10 level of the AHA-1542B firmware. I am not sure just where though. The present latest AHA-1542B firmware is version 3.20, and supports drives up to 8GB under MS-DOS. Table of Contents ==== QUESTION: What are the differences between the Adaptec 1542B and the 1542C? ANSWER from: Terry Kennedy (terry@spcvxa.spc.edu) ==== The 1542C is an an updated model which replaces the 1542B. The 1542C features jumperless setup, having only 8 DIP switches. All other configuration options are set using the 1542C's built-in BIOS configuration utility. Configurable features not found on the 1542B are: Ability to enable/disable sync negotiation on a per-ID basis (the 1542B could only do it for all ID's on the SCSI bus) Ability to send "start unit" commands on a per-ID basis BIOS works with alternate I/O port settings on the adapter. Ability to boot from ID's other than 0 Software-selectable termination Software-selectable geometry translation Additional DMA speeds of 3.3 and 10 MB/sec Additionally, the 1542C uses a Z80 CPU and 8Kb buffer instead of an 8085 and 2Kb buffer as on the 1542B. Table of Contents ==== QUESTION: What are the differences between the 1542C and the 1542CF? ANSWER from: Terry Kennedy (terry@spcvxa.spc.edu) ==== The 1542CF includes all of the 1542C features, and adds "Fast" SCSI operation, providing SCSI data rates of up to 10MB/sec (compared with an upper limit of 5MB/sec on the 1542C). This is unrelated to the host DMA rate. It also has a software configurable address for the floppy controller and a "self-healing" fuse for termination power. Table of Contents ==== QUESTION: Where can I get SCSICNTL.EXE and other Adaptec files? ANSWER From: randy@psg.com (Randy Bush) and Timothy Hu timhu@ico.isc.com ==== ftp.psg.com:~/pub/adaptec/... SCSICNTL.EXE.Z adse.dd adse.dd.readme list os2drv.zip scsi_drv.Z scsi_drv.readm update.pkg.Z "list" is a file that describes all the files in this directory. You can get the ASPI specs from Adaptec's Bulletin Board (408)945- 7727. [Editor(GF): You can also get ASPI spec's from Adaptec's WWW server.] Table of Contents ==== QUESTION: What kinds of Optical Drives are available? The previousanswer From: joungwoo@mensa.usc.edu (John Kim) has been replaced with an updated version. ANSWER From: Psycho Bob <honge@creighton.edu>[Editor(GF)] DATE: Sep 18, 1996 ==== As magnetic recording approaches the current engineering limit, more and more attention is paid to optical storage solutions. Optical storage has good points going for it -- immunity to stray magnetic field, potential for higher storage capacity per unit area, and relatively low media cost. Although CD-ROM and CD-R are also optical storage units, they are not rewritable -- that puts them out as either secondary storage or primary backup storage for most of us. There is an upcoming sub-format called CD-E ("E" for erasable) that is suppose to become available in late 1996, but I haven't seen much news or even definite rumors. With the advent of DVD, the CD-E may only be a temporary stepping stone to recordable DVDs. Currently, the most popular magnetic storage format is magneto- optical (MO) format. It was the only popular rewritable optical storage disc technology before Panasonic's phase-change double-function (PD) format came out in 1995. Magneto-Optical As the name implies, MO uses both magnetic and optical technology to store data on the disc. The disc itself is rare earth metal substrate. When data is to be written, the particular spot is first heated by the laser to the Curie point, and the magnetic field is generated while the spot cools. By varying the magnetic field angle, the substrate is polarized in certain way that it will reflect the laser beam differently depending on the magnetic field angle when the particular spot was cooling down. MO comes in many sizes and capacities. Consumers were first exposed to MO in Steve Jobs' NeXT computer in the mid-1980s. Although 5.25" had a slow start due to initial high cost, it has been evolving quite nicely. The more popular ISO capacities for 5.25" MO are 2.4GB/2.6GB, 1.2GB/1.3GB, and the 600MB/650MB. In 3.5" form, MO is available in 540MB/640MB, 230MB, and the 128MB. There are also some 12" MO, 14" MO, and other odd sizes in odd capacities. But they are limited to niche markets. Sony MiniDisc-Data Derived from the Mini-Disc (MD) audio format Sony introduced, MD-Data is to MD as CD-ROM is to digital audio compact disc (CD-DA). MD-Data (and digital audio MD) is based on the same magneto-optical technology, which explains the high-cost of the consumer MD audio units. MD-Data is the smallest of the MO family. With 2.5" form factor, it can store 140MB of uncompressed data. Current MD-Data drives are rather slow at 150KB/sec sustained transfer rate, but Sharp is hoping to change that. Sharp will (hopefully) ship a 300KB/sec by the end of 1996, with a second generation of MD-Data available by sometime in 1997. The current schedule from Sharp indicates the second generation MD-Data will be able to store up to 700MB with 600KB/sec transfer rate. The most important technical advancement MD-Data brought for MO in general is the one-pass recording. Prior to 5.25" 2.4GB/2.6GB MO and 3.5" 540MB/640MB MO, almost all MO used two passes to write data onto the disc -- one pass to erase the whole track, and a second pass to write the updated data. MD's one pass recording, called light intensity modulation, direct over-write (LIM-DOW, ISO 14517) will be in almost all the future MO formats until another better technology comes along. Just like CD, MD-Data comes in various flavors -- rewritable, write- once, and read-only cartridges. There is also a hybrid disc for MD and MD-Data that is part read-only, and part rewritable. Panasonic phase-change double-function (PD) In around mid-'95, Panasonic released a proprietary optical storage format called phase-change double-function (PD) drive. The PD uses substrate that will reflect the light differently when heated to different temperatures. Write-once-read-multiple (WORM) drives were actually the first phase-change formats, but PD is the first *reversible* (that is, re-writable) phase-change format. Current PD stores 650MB per PD cartridge. Currently, PD's only advantage over its MO brethren is the PD drive's ability to read regular CD-DA and CD-ROMs. The PD rewritable cartridge is not usable in regular CD-ROM drives. WORM and CD-R Both write-once-read-multiple (WORM) and compact disc recordable (CD- R) are both write-once formats -- once you have written the data to the disc, the data cannot be changed. Put another way, the disc media can only be used once. For long term archival of data that need not be changed, it makes sense -- as CD-R media price is unbeatable [As of mid 1996, 650 MB CD-R media sells for $6 to $8 each or about 1 cent per MB!] . Current CD-R offers maximum of 650MB per disc. WORM was the first popular format for optical storage, before being eclipsed by MO. WORM is still used by big companies and the government for archival purposes since it has the characteristic of not being able to be altered wihout damaging the media (good audit trail). The new WORM formats being introduced are tending to be more proprietary. There is rarely any interchangability between different vendor's drives and media. During the WORM to MO transition, a curious format called continuous composite write-once (CCW) appeared. CCW cartridges function as WORM cartridges, writable using the installed base of WORM drives. But put it into MO drive, CCW cartridges becomes rewritable. Simply put, CCW is MO in WORM's clothing. Many of today's 5.25" MO drives still have the capability to read CCW cartridges. The future Almost all the formats mentioned above have future plans -- usually an "improved version" with faster and more storage capacity. The 5.25" MO camp is shooting for the 4.8GB/5.2GB range, with faster sustained transfer rate in writing data. 3.5" may double their 650MB soon by using both sides of the disc. PD may also double the storage space by using both sides of the disc. But currently it's doubtful as DVD has pretty much been finalized. It'll be interesting to see how Panasonic will interpret the PD in the DVD marketplace (DVD-PD?). DVD-RAM is rumored to use phase-change technology. The same goes for CD-E, the latecomer of the bunch. If the CD-E is truly playable in ordinary CD-ROM (and audio CD player), it'll probably become the optical storage standard in all but the high- capacity, high-end/server market. Format Phys. Capacity Bytes # of sides Capacity Standard size per disk per sector per side MO 1p 2.5" 140MB 2048/2336 single 140MB Sony MD-Data MO 2p 3.5" 128MB 512 single 128MB ISO/IEC 10090, ECMA 154 MO 2p 3.5" 230MB 512 single 230MB ISO/IEC 13963, ECMA 201 MO 1p 3.5" 540MB 512 single 540MB DIS(ISO/IEC) 15041 640MB 2048 single 640MB MO 2p 5.25" 600MB 512 dual 296MB ISO/IEC 10089 650MB 1024 dual 322MB ANSI X3.2121-1992 MO 2p 5.25" 1GB 512 dual 463MB ISO 13481 1GB 1024 dual 510MB MO 2p 5.25" 1.2GB 512 dual 595MB ISO/IEC 13549 1.3GB 1024 dual 650MB ECMA 184 MO 1p 5.25" 2.4GB 512 dual 2.298GB DIS(ISO/IEC) 14517 2.6GB 1024 dual 1.3GB MO 2p 5.25" 1.5GB 4096 dual 750MB Panasonic MO 1p 5.25" 4.6GB 1024 dual 2.3GB Pinnacle Micro "Apex" MO 12" 8GB Nikon MO 12" 3.2GB Sony MO 14" 6.8GB 1024 dual 3.4GB Kodak System 2000 10.2GB 1024 dual 5.1GB 14.8GB 1024 dual 7.4GB WORM 5.25" 2.6GB DIS(ISO/IEC) 15486 WORM 5.25" 650MB single 650MB ISO/IEC 9171 Format A WORM 5.25" 470MB Panasonic 940MB 1.4GB WORM 12" 15GB Sony PD 1p 5.25" 650MB 4096 single 650MB Panasonic CD-R 5.25" 550MB 2048 single 553MB 650MB 2048 single 650MB CD-E 5.25" 650MB pending... *technology: 1p -- one-pass write 2p -- two-pass write Standards for storage are set by many organizations. International Standards Organization (ISO), European Computer Manufacturers Association (ECMA), Deutsche Institut fur Normung (DIN), Japanese Industrial Standards Committee (JISC), and American National Standards Institute (ANSI) set the main optical disc storage standards. The ISO standards take precedence over all other standards. In the above table, the heading defines one standard -- e.g. 5.25" MO 1.2GB/1.3GB has both ISO 13549 and ECMA 184 listed for it. IT IS NOT THAT 1.2GB FOLLOWS ISO 13549 AND 1.3GB FOLLOWS ECMA 184. Of CD standards... Funny as it seems, CD is actually considered as proprietary a format made by Sony and Phillips. The physical format for derivatives like CD-ROM and CD-R are "written in mutual agreement" in form of Red Book, Yellow Book, Orange Book, etc. Of bytes/sector and usability... As many of you might notice (especially on 5.25" MOs), there are different sized sectors. Many O/Ses assume one sector to contain 512 bytes. If you buy any of the media that use different than 512 byte/sector, you will need a software driver of some sort to use the media. In optical media, the sectors are "hard sectored" at factory -- in other words, you cannot change the number of sectors by reformatting (low-level formatting) them. Take the 5.25" 1.2GB/1.3GB MO for example again. The 1.3GB media is sectored at 1024 bytes per sector. So the 1.3GB media has total of 637,041 sectors (per side) on it. If you do not use a software driver and your operating system does not properly recognize it, the 1.3GB media will become a 650MB cartridge (~325MB per side)!! The safest bet is to use the 512 bytes/sector media. That should make the drive and media usable on most operating systems. Addendum: (11/15/96) Sony and Phillips have just announed finalization of compact disc re-writable (CD-RW), together with HP, Matsushita, etc. Long story short, the CD-RW uses phase-change media -- same as Panasonic proprietary PD format. Not only that, it also stores 650MB like PD. And also like the PD, the CD-RW media cannot be read in regular CD and CD-ROM drives (surprise!)!! So, the good news is that CD-RW is here. The bad news is that it's as proprietary as Panasonic's PD in compatibility with current installed base of CD and CD-ROM players. Table of Contents ==== QUESTION: Where can I get various SCSI documentation? ==== Thanks to John Lohmeyer of Symbios Logic, a number of SCSI related files are available for anonymous ftp. The archive contains a large amount of data relating to SCSI, and ESDI as well as SCSI-2, IPI, and Fiber Channel, as well as the last revision of the SCSI-1 and SCSI-2 standards before they went into publication by ANSI. This information server is maintained by Symbios Logic (formerly NCR Corp., formerly AT&T Global Information Solutions) in the hope of returning some value to the Internet community. It contains information about commercial products, and also about computing- related topics in which Symbios Logic as a company, or individuals therein, have interest and expertise. The information is accessible from several sources: SCSI BBS: (719) 574-0424 anonymous ftp to ftp.symbios.com WWW: http://www.symbios.com/x3t10 Table of Contents ==== QUESTION: How can I find out about the emerging SCSI standards? ANSWER From: Milton Scritsmier (milton@arraytech.com) ==== The X3T10 committee has opened up a WWW site. It has an overview of SCSI-3, as well as pointers to the WWW sites for the three serial interfaces (FC, SSA, and P1394), and a pointer to an online copy of a proposed SCSI-2 spec. Here is the original announcement: Subject: New X3T10 Home Page Date: Thu, 31 Aug 95 14:07:00 MDT With a LOT of help from Carey Harrington (Thank you!), X3T10 now has a World Wide Web home page. If you have a web browser, you may want to check out: http://www.symbios.com/x3t10 John Lohmeyer, Chair X3T10 Technical Committee ANSWER #2 From: Gary Bartlett (garyb@abekas.com) A draft version of the SCSI-2 spec is in HTML form on the WWW at: http://abekas.com:8080/SCSI2/ ANSWER #3 From: Gary Watson (trimm@netcom.com) Small Form Factor (SFF) Committee documents are available by FaxAccess at: (408) 741-1600 You will be asked to order documents by number. For example: to get information on the Single Connector Attach spec. The SCA-1 spec. is document #8015 The SCA-2 spec. is document #8046 document #8000 is and index to the other documents. [Editor(GF): you might try: http://playground.sun.com/pub/SCA/SCAR3- 2.txt ] This FaxAccess service is available to all, but please keep in mind that unless you have engineering-level understanding of peripheral interfaces, you _will_not_ be able to understand any of it and you are wasting your own time and the bandwidth of these resources. If you are trying to learn more about SCSI, you are better off reading the magazine articles and books listed elsewhere in this FAQ. The SCSI, SFF, SSA, and Fibre Channel reflectors: A list of these is available on the Symbios WWW site. "The SCSI, SFF, SSA, and Fibre Channel reflectors are for review and commentary on the respective specifications, not for asking questions about the interfaces (unless related to a specific ambiguity in a specification) nor for recruiting nor for technical support nor any purpose other than what is stated. The reflectors _are_ available for public review and commentary as required by ANSI and ISO." Any spec on the reflectors or on the bbs or on the ftp sites are **proposed** or **preliminary** and are often subject to major substantive changes during the committee process. Actual, released, final specs are *only* available from Global Engineering Documents. ANSWER #4 From: Gary Field(gfield@zk3.dec.com) For Fibre Channel Association: http://www.fibrechannel.com/ Table of Contents ==== QUESTION: Where can I get official ANSI SCSI documents? ANSWER #1 From: kev@hpcpbla.bri.hp.com (Kevin Jones) and jmatrow@donald.WichitaKS.NCR.COM (John Matrow) ==== The SCSI specification: Available from: ANSI 11 West 42nd St. - 13th floor New York, NY 10036 Sales Dept. (212) 642-4900 OR Global Engineering Documents 15 Inverness Way East Englewood Co 80112-5704 (800) 854-7179 or (303) 792-2181 Int'l Sales Fax: (303) 397-2740 SCSI-1: X3.131-1986 SCSI-2: X3.131-199x SCSI-3 X3T9.2/91-010R4 Working Draft [Editor(GF):] The official ANSI standards are NOT available free of charge from any source. Only draft versions are freely distributable. Table of Contents ==== QUESTION: What SCSI books and tutorials are available? ANSWER From: Gary Field (gfield@zk3.dec.com) IN-DEPTH EXPLORATION OF SCSI can be obtained from Solution Technology, Attn: SCSI Publications, POB 104, Boulder Creek, CA 95006, (408)338-4285, FAX (408)338-4374 THE SCSI ENCYLOPEDIA and the SCSI BENCH REFERENCE can be obtained from ENDL Publishing, 14426 Black Walnut Ct., Saratoga, CA 95090, (408)867-6642, FAX (408)867-2115 SCSI: UNDERSTANDING THE SMALL COMPUTER SYSTEM INTERFACE was published by Prentice-Hall, ISBN 0-13-796855-8 (Seems to be out of print) A neat little book called "Basics of SCSI" second edition, was sent to me free of charge by Ancot Corporation, Menlo Park, CA (415) 322- 5322. It gives a simplified description of how most aspects of the SCSI bus work and includes some discussion of SCSI-2 issues. "The book of SCSI - A guide for Adventurers" by Peter M. Ridge. Published by No Starch Press, Daly City, CA, ISBN # 1-886411-02-6, List Price $34.95. Contains general coverage of most aspects of SCSI. http://www.nostarch.com/scsi.htm "Programmer's Guide to SCSI" with CDROM - by Brian Sawert. Published by Addison Wesley, Reading, MA. SRP $39.95 ISBN # 0-201-18538-5 Includes a chapter on UNIX SCSI subsystems written by Gary Field. http://cseng.awl.com/bookdetail.qry?ISBN=0-201-18538-5&ptype=0 Addition by: (kyrrin2@wizards.net) 'The SCSI Bus and IDE Interface' 2nd edition by Friedhelm Scmidt, Addison-Wesley Publishing, $34.95 (I think). It includes a diskette with examples of source code to handle SCSI and IDE devices from a low-level programmer's perspective, and it has very detailed technical descriptions of both subsystems. Not a book for beginners, but I heartily recommend it for anyone who's serious about learning the technical ropes. ANSWER #2 From: Runar Jorgensen (runar.jorgensen@fys.uio.no) There was a two part article in Byte Magazine. The first part was in Feb 1990 issue, p. 267-274 and the second was in Mar 1990 issue, p. 291-298. Another two part article appeared in Byte in May 1986 and June 1986. Table of Contents ==== QUESTION: Where can I find SCSI info on the Web? ANSWER FROM: Gary Field (gfield@zk3.dec.com) Try some of these: http://www.delec.com/Tech_Links/SCSIGuide/ http://www.quantum.com/src/ Table of Contents ==== QUESTION: Where can I get information on various disk drives and controllers? ANSWER: ekrieger@quasar.xs4all.nl (Eric Krieger) (Updated Sep. 30, 1994) ==== Drive and Controller Guide, Version 4.3 THEREF(tm) is a comprehensive Directory of Hard Drives, Floppy Drives, Optical Drives, and Drive Controllers & Host Adapters. It is designed to help the novice and pro alike with integration problems and system setups. Information is provided in two handy formats; Portrait mode, for those who prefer a normal book-binding type print format, and(or) do not have a printer with Landscape capability. And Landscape mode, for those who pre-fer a computer-printout type format. For printing, a Laserjet is preferred, but not necessary, and setup info is provided. For viewing, LIST(tm) by Vernon Buerg, will provide an excellent result, and allow text searches for finding specific models. By F. Robert Falbo Due many reports about the unavailablity of this file/archive I made sure that the file does exist at the following site: ftp://ftp.funet.fi you should find the archive at: /pub/doc/hardware/harddisks/theref43.tar.gz /pub/doc/hardware/harddisks/theref43.readme (In that directory-path there is also a sub-directory Seagate, where you also can find info/files about Seagate-drives). Before you actually get this file, be sure to get/read the file /README.FILETYPES since it explains the used file-extension and which (de-)archiver should be used (and where to find/get them!). Note: In the archive there are files containing Extended ASCII or ANSI characters (mostly used with IBM- and compatible PC's), so it may be a bit unreadable when reading it on non-PC systems, or without using a proper Characterset/Font! TheRef is also available via WWW from: http://theref.c3d.rl.af.mil Table of Contents ==== QUESTION: Where can I get technical information and jumper settings for HP drives ? ANSWER From: Rodney Brown (RBrown@cocam.com.au) Update From: Martin C Mueller (mcm@mathematik.uni-kl.de ) ==== HP SCSI Storage Device Support Pages http://www.hp.com/isgsupport/index.html Table of Contents ==== QUESTION: How can I contact Adaptec? Also: Future Domain, Corel CD Creator, Trantor, Incat systems, Symbios Logic. ANSWER From: jcaples@netcom.com (Jon D Caples) ==== 408 945-8600 Main number 800 959 7274 tech support 800 442 7274 orders, doc, new bios, etc. 408 945-7727 BBS Adaptec's general inquiry number, 800-959-7274, affords access to a FAX-based information retrieval system. In order to preserve the accuracy of this information, I won't go into details about how to use it (since Adaptec may change things without telling me :) ). For those outside the CAN-US area, or local to Adaptec the direct FAX info number is (408) 957-7150. There are three general topics as of this writing: General Information Sales Information Technical Information Give it a call and request the directory! As of this writing there are over 130 documents available. You need a touchtone phone and the fax number. You'll also be asked for an extension number to stamp on the FAX which will be used to identify the recipient. [Editor(GF): As of July 1993 Adaptec bought Trantor. Try (800) 872-6867 (TRA-NTOR)] [Editor(GF): As of Feb. 19, 1998, Adaptec bought Symbios Logic] World Wide Web (WWW) URL: http://www.adaptec.com/ [(from: Andrew Lockhart (andrew@interact.manawatu.planet.co.nz) ] You can address Adaptec support by email. The address is support@adaptec.com. An auto-responder will bounce a message back acknowledging receipt of your email. This message will also detail other current forms of Adaptec Technical support. They promise a, no more than, 5 day turn-around. We have found the response brief, but satisfactory to our needs. We should add, we mention we are Dealers in our email (which may improve Adaptecís response). Table of Contents ==== QUESTION: How can I contact Archive Corporation? ==== [Editor(GF)] Archive was bought by Conner Peripherals in 1993 Table of Contents ==== QUESTION: How can I contact BusLogic /Bustek / Mylex ? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== Mylex Corp. 34551 Ardenwood Blvd. Fremont, CA 94555 (510) 796-6100 Tech. Support: Voice: (510) 608-2400 FAX: (510) 745-7715 Email: for HBA: techsup@mylex.com For RAID: support@mylex.com WWW: http://www.mylex.com/ Table of Contents ==== QUESTION: How can I contact Corel? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== Main Number: (800) 772-6735 Tech. Support: (613) 728-1010 ANSWER From: Gerrit Visser (gerrit@isgtec.com) ==== WWW: http://www.corel.ca/ ftp: ftp.corel.ca: /pub SCSI is under Multimedia For Corel CD Creator Software contact Adaptec Table of Contents ==== QUESTION: How can I contact Fujitsu? ANSWER From: Ken Porter (72420.2436@compuserve.com) ==== Fujitsu FactsLine FAX Back service (408) 428-0456 A six page catalog of available documents can be ordered. ANSWER From: Mike Henry (anonymous) A while back, Fujitsu created a product called Fujitsu Knowledge System (FKS) (long available on Compuserve (GO FUJITSU)). It is a Windows Help File (.HLP) listing of many Fujitsu disk, tape, and optical products. It includes drive switch/jumper settings and meanings (lot of posts requesting this info). It is available via anonymous ftp from ftp.intellistor.com in the /pub/fks directory filename: fks.exe It is self-extracting and mostly self-documenting. Table of Contents ==== QUESTION: How can I contact Quantum? ANSWER From: kmartine@qntm.com (Kevin Martinez) ==== Quantum Corporation 500 McCarthy Blvd. Milpitas, CA 95035 Technical Support Telephone Numbers: 800 826-8022 Main Technical Support Number 408 894-3282 Technical Support Fax 408 894-3214 Technical Support BBS V.32 8N1 408 434-9262 Technical Support for Plus Development Products 408 894-4000 Main Quantum Phone number 800 4DISKFAX FAX on demand (From Thanh Ma tma@encore.com) WWW: http://www.quantum.com/ Table of Contents ==== QUESTION: How can I contact Seagate? ANSWER From: landis@sugs.tware.com (Hale Landis) ==== Here are the numbers for Seagate's Technical Support. SeaBOARD - Bulletin Board System available 24 hours. Use 8 data bits, no parity, 1 stop bit (8-N-1). USA/Canada 408-438-8771 9600 baud* England 44-62-847-8011 9600 baud* Germany 49-89-140-9331 2400 baud* Singapore 65-292-6973 9600 baud* Australia 61-2-756-2359 9600 baud* * - Maximum baud rate supported. SeaFAX 408-438-2620 Use a touch-tone phone to have information returned to you via FAX. Available 24 hours. Technical Support Fax 408-438-8137 FAX your questions or comments 24 hours. Responses are sent between 8:00AM and 5:00PM PST Monday through Friday. SeaFONE 408-438-8222 Provides recorded information 24 hours or talk to a technical specialist between 8:00AM to 5:00PM PST Monday through Friday. SeaTDD 408-438-5382 Using a Telecommunications Device for the Deaf, you can send questions or comments 24 hours or have a dialog with a technical support specialist between 8:00AM and 5:00PM PST Monday through Friday. WWW: http://www.seagate.com/ Table of Contents ==== QUESTION: How can I contact Conner Peripherals? ==== Conner Peripherals was bought by Seagate Table of Contents ==== QUESTION: How can I contact Maxtor? ANSWER From: David G North (D_North@tditx.com) ==== Main Number: (800) 262-9867 (Has FAXback feature for drive info etc) ftp site: ftp.maxtor.com (New!) ANSWER From: Eric Van Buren (vanburen%flovax.dnet@rocdec.roc.wayne.edu) ==== WWW: http://www.maxtor.com/ Table of Contents ==== QUESTION: How can I contact NCR? ==== NCR Microelectronics division was bought by AT&T and then by Symbios Logic. See "How can I contact Symbios Logic" As of Feb 19, 1998, Hyundai agreed to sell Symbios to Adaptec. Table of Contents ==== QUESTION: How can I contact Philips? ANSWER From: S. C. Mentzer (smentzer@anes.hmc.psu.edu) ==== Philips Consumer Electronics Co. One Philips Drive Knoxville, TN 37914-1810 (615) 521-4316 (615) 521-4891 (FAX) [Editor(GF)] WWW: http://www.philips.com/ Table of Contents ==== QUESTION: How can I contact Symbios Logic? Answer From: Symbios Logic Update From: Wade Adams (link@vantek.net) ==== Symbios is a wholly owned subsidiary or Hyundai Elecctronics. For literature on any Symbios Logic product please contact: Phone: (800) 636-8022 (800) 856-3093 (719) 536-3300 Fax: (719) 536-3301 email: literature@symbios.com Technical Support: Phone: (719) 533-7230 WWW: http://www.symbios.com/ Table of Contents ==== QUESTION: How can I contact UltraStor? (Out of business) Answer From: Ultrastor ==== UltraStor Corporation 13766 Alton Parkway suite 144 Irvine, CA 92718 General (714) 581-4100 Tech. Support (714) 581-4016 FAX (714) 581-4102 BBS (714) 581-4125 email: ultrastor@primenet.com finger: ustor@primenet.com ftp: ftp.primenet.com:users/u/ustor ==== Answer From: Ben Mehling (bmehling@uci.edu) ==== I am setting up a "unauthorized" UltraStor site for the orphaned customers and cards still out there. I do not think the above numbers are good anymore. The 4100 line will get you Power I/O (an unrelated Adaptec holding) and the 4016 line may get you a dead-end answering service. The company is no longer active (as far as I know). The primenet account is alive, but again not active. These links are to the "Unauthorized" UltraStor site. This site is in no way affiliated with UltraStor or its holding companies. It is a free "mirror" site for distribution of drivers and information. (hint: we are trying to help out, not provide tech support.) Try: UltraStor@kuci.uci.edu (unauthorized). www.UltraStor (unauthorized). ftp.UltraStor (unauthorized). The above three addresses are hypertext linked to these addresses: The web site address is: www.kuci.uci.edu/~ustor The FTP site address is: falco.kuci.uci.edu/users/ustor The mail/finger address is ultrastor@kuci.uci.edu / ustor@falco.kuci.uci.edu The current maintainers are: Ben Mehling (bmehling@uci.edu) Phil Colline (pcolline@falco.kuci.uci.edu) Table of Contents ==== QUESTION: How can I contact Tecmar Technologies (formerly Wangtek, WangDAT, Sytron, and Rexon)? ANSWER FROM: from: Jay Long - (jayl@mfltd.co.uk) and Peter Dyballa (pete@riese.thi.informatik.uni-frankfurt.de) ==== Tecmar Technologies, Inc. 1900 Pike Rd., Bldg. E Longmont, CO USA phone: (303) 682-3700 (303) 776-7706 FAX: (303)776-1085 faxback: (800) 4BACKUP WWW: http://www.tecmar.com/ European Office Unit 15 Suttons Business Park Suttons Park Avenue Earley, Reading, UK RG6 1AZ (44) 1189-660063 (44) 1189-660065 FAX Singapore Office Blk. 35 Marsiling Industrial Estate Road 3 #05-01/ 06 Singapore 739257 (65) 269-2228 (65) 360-0888 fax Table of Contents ==== QUESTION: How can I contact Western Digital? ANSWER From: FILIPG@PARANOIA.COM ==== Address: Western Digital Corporation 8105 Irvine Center Drive Irvine, CA USA 92718 Online Services: Tech Support BBS 714-753-1234 (up to 28.8 KBS) WWW: http://www.wdc.com/ FTP ftp.wdc.com AOL (keyword) WDC or Western Digital MSN (go word) WDC Table of Contents ==== QUESTION: How can I contact DPT (Distributed Processing Technology)? ANSWER: From: Gary Field (gfield@zk3.dec.com) ==== voice: (407) 830-5522 FAX: (407) 260-6690 [Editor(GF)] WWW: http://www.dpt.com/ Table of Contents ==== QUESTION: How can I contact Micropolis? ANSWER: From: Richard Ravich (Richard_Ravich@microp.com) ==== Tech Support: (818) 709-3325 email: Richard_Ravich@microp.com WWW: http://www.micropolis.com/ [Editor(GF): I believe that Micropolis is now (late 1997) out of business Ė RIP. You might try http://www.blue-planet.com/tech/ for drive info. ] Table of Contents ==== QUESTION: How can I contact Legacy Storage Systems ? ANSWER: From: Gregory Smith (GREGS@lss-chq.mhs.compuserve.com) ==== General: (905) 475-1077 Sales/Tech support/Service: (905) 475-0550 U.S. Tech Support: (800) 361-5685 Fax: (905) 475-1088 Mail: Legacy Storage Systems 43 Riviera Drive Markham, ON Canada L3R 5J6 Table of Contents ==== QUESTION: what is FAST SCSI? ANSWER From: kev@hpcpbla.bri.hp.com (Kevin Jones) ==== There are 2 handshaking modes on the SCSI bus, used for transferring data: ASYNCHRONOUS and SYNCHRONOUS. ASYNCHRONOUS is a classic Req/Ack handshake. SYNCHRONOUS is "sort of" Req/Ack, only it allows you to issue multiple Req's before receiving Ack's. What this means in practice is that SYNCHRONOUS transfers are approx 3 times faster than ASYNCHRONOUS. SCSI1 allowed asynchronous transfers at up to 1.5 Mbytes/Sec and synchronous transfers at up to 5.0 Mbytes/Sec. SCSI2 had some of the timing margins "shaved" in order that faster handshaking could occur. The result is that asynchronous transfers can run at up to 3.0 Mbytes/Sec and synchronous transfers at up to 10.0 Mbytes/Sec. The term "FAST" is generally applied to a SCSI device which can do syncrhonous transfers at speeds in excess of 5.0 Mbytes/Sec. This term can only be applied to SCSI2 devices since SCSI1 didn't have the timing margins that allow for FAST transfers. Table of Contents ==== QUESTION: How can I check a passive SCSI terminator? ANSWER From: stevel@coos.dartmouth.edu (Steve Ligett) ==== With an Ohmmeter: The terminator contains 18 220-ohm resistors from signals to TERMPWR, and 18 330-ohm resistors from those signals to GROUND. I've drawn that below: TERMPWR --+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | | | | | | | | | | | | | | | | | R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 | | | | | | | | | | | | | | | | | | sig o o o o o o o o o o o o o o o o o o | | | | | | | | | | | | | | | | | | R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 | | | | | | | | | | | | | | | | | | --+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ GROUND R1 = 220 Ohms, R2 = 330 Ohms When you measure from any one signal to termpower, you aren't measuring that resistor in isolation, you are measuring that resistor IN PARALLEL with the combination of the corresponding 330 ohm resistor plus 17 220+330 ohm resistor pairs in series. I've redrawn the schematic to make this easier to see: TERMPWR /+---+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | | | | | | | | | | | | | | | | | | R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 R1 | | | | | | | | | | | | | | | | | | | o o o o o o o o o o o o o o o o o | | | | | | | | | | | | | | | | | | | R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 R2 | | | | | | | | | | | | | | | | | | | --+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | / GROUND R1 | | | | R2 | / o <--------- 17 other pairs in parallel ----------> sig We're trying to measure that one resistor from a signal to TERMPWR, but there's a ton of other stuff in parallel. The resistance of that "stuff" is 330 + 550/17 ohms (the 330 ohm resistor, in series with a parallel combination of 17 550 ohm resistors). The general formula for the equivalent of two resistances in parallel is r1*r2/(r1+r2). Whipping out my trusty spreadsheet, I find that the "stuff" has a resistance of about 362 ohms, and that, in parallel with 220 ohms is about 137 ohms. Table of Contents ==== QUESTION: Can someone explain to me the difference between 'normal' SCSI and differential SCSI? ANSWER From: ralf@wpi.WPI.EDU (Ralph Valentino) ==== "Normal" SCSI is also called "Single-ended" SCSI. For each signal that needs to be sent across the bus, there exists a wire to carry it. With differential SCSI, for each signal that needs to be sent across the bus, there exists a pair of wires to carry it. The first in this pair carries the same type of signal the single-ended SCSI carries. The second in this pair, however, carries its logical inversion. The receiver takes the difference of the pair (thus the name differential), which makes it less susceptible to noise and allows for greater cable length. Table of Contents ==== QUESTION: What are the pinouts for differential SCSI? ANSWER From: ralf@wpi.WPI.EDU (Ralph Valentino) ==== Differential SCSI Connector Pinouts ---------------------------------------- ---------------------------- ------------ | SCSI | | MINI | | | SCSI | | MINI | | | SIGNAL | DD-50P | MICRO | DD-50SA | | SIGNAL | DD-50P | MICRO | DD-50SA | ---------------------------------------- ---------------------------- ------------ | -GND | 2 | 26 | 34 | | (open) | 1 | 1 | 1 | | -DB(0) | 4 | 27 | 2 | | +DB(0) | 3 | 2 | 18 | | -DB(1) | 6 | 28 | 19 | | +DB(1) | 5 | 3 | 35 | | -DB(2) | 8 | 29 | 36 | | +DB(2) | 7 | 4 | 3 | | -DB(3) | 10 | 30 | 4 | | +DB(3) | 9 | 5 | 20 | | -DB(4) | 12 | 31 | 21 | | +DB(4) | 11 | 6 | 37 | | -DB(5) | 14 | 32 | 38 | | +DB(5) | 13 | 7 | 5 | | -DB(6) | 16 | 33 | 6 | | +DB(6) | 15 | 8 | 22 | | -DB(7) | 18 | 34 | 23 | | +DB(7) | 17 | 9 | 39 | | -DB(P) | 20 | 35 | 40 | | +DB(P) | 19 | 10 | 7 | | GND | 22 | 36 | 8 | |DIFSENS | 21 | 11 | 24 | | GND | 24 | 37 | 25 | | GND | 23 | 12 | 41 | |TERMPWR | 26 | 38 | 42 | |TERMPWR | 25 | 13 | 9 | | GND | 28 | 39 | 10 | | GND | 27 | 14 | 26 | | -ATN | 30 | 40 | 27 | | +ATN | 29 | 15 | 43 | | GND | 32 | 41 | 44 | | GND | 31 | 16 | 11 | | -BSY | 34 | 42 | 12 | | +BSY | 33 | 17 | 28 | | -ACK | 36 | 43 | 29 | | +ACK | 35 | 18 | 45 | | -RST | 38 | 44 | 46 | | +RST | 37 | 19 | 13 | | -MSG | 40 | 45 | 14 | | +MSG | 39 | 20 | 30 | | -SEL | 42 | 46 | 31 | | +SEL | 41 | 21 | 47 | | -C/D | 44 | 47 | 48 | | +C/D | 43 | 22 | 15 | | -REQ | 46 | 48 | 16 | | +REQ | 45 | 23 | 32 | | -I/O | 48 | 49 | 33 | | +I/O | 47 | 24 | 49 | | GND | 50 | 50 | 50 | | GND | 49 | 25 | 17 | ---------------------------------------- ---------------------------- ------------ Please note that I can only verify the DD-50P connector. The Mini Micro and DD-50SA pinout above is a pin for pin mapping from the SCSI pinout in this FAQ. ==== How can I tell if I have a single ended or a differential drive? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== Most times the model number of the drive will end with "D". Use an ohm meter to check the resistance between pins 21 & 22. On a single ended system, they should both be tied together and tied to GND. On the differential drive, they should be open or have a significant resistance between them. Differential drives are less common than single-ended ones, because they are mainly used only where longer cable runs are necessary, and they are not generally used in PCs, but state of the art drives are available with differential interfaces. Generally only the higher performance drives have a differential option because of the added cost. Table of Contents ==== QUESTION: Who manufactures SCSI extenders and Single-Ended to Differential converters ? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== The following companies manufacture SCSI extenders and converters: Ancot Corporation 115 Constitution Drive Menlo Park, CA 94025 Tel: (415) 322-5322 Fax: (415) 322-0455 Email: sales@ancot.com URL: http://www.ancot.com/ Apcon Inc. 17938 SW Boones Ferry Road Portland, OR 97224 Phone: (503) 639-6700 Fax: (503) 639-6740 Email: info@apcon.com URL: http://www.apcon.com/ Paralan Corporation 7875 Convoy Court, San Diego, CA 92111 Tel. (619) 560-7266 || Fax 619-560-8929 WWW: http://www.paralan.com/ email: scsi@paralan.com Rancho Technology Inc. 10783 Bell Court-Rancho Cucamonga-CA-91730 Phone: (909)987-3966; Fax: (909)989-2365; E-Mail: scsi@rancho.com; BBS: (909)980-7699 URL: http://www.rancho.com/ Table of Contents ==== QUESTION: I've got a SCSI disk with an 80 pin connector. Someone called it an SCA drive. Can I connect this to my SCSI bus? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== SCA Stands for "Single Connector Attachment". It is a standard being worked on by the ANSI Small Form Factor (SFF) committee. It combines WIDE SCSI signals, Power connections and ID switch connections onto one connector. SCSI vendors sell adapters that bring out the three sets of signals to conventional connectors. See: http://playground.sun.com/pub/SCA/SCAR3-2.txt for more information about SCA. Table of Contents ==== QUESTION: What are the pinouts for SCSI connectors? ANSWER From: snively@scsi.Eng.Sun.COM (Bob Snively) [ Edited and expanded by Gary Field (gfield@zk3.dec.com) ] ==== Originally dated May 23, 1990 The connector families described by the drawings have standard pin numberings which are described the same way by all vendors that I have encountered. The SCSI-2 specification identifies the standard numbering, using that convention. It happened to be documented by AMP, but all the vendors use the same convention. The following diagrams have the outline drawings of connector sockets at the bottom. This is really for reference only, because the connector sockets and plugs are both specified as to their numbering and usually are labeled. There are some minor problems in naming the microconnector conductor pairs, which I have corrected in the enclosed diagram. All the conductor pairs of the Mini-Micro (High Density) connector are in fact passed through on the cables. SCSI-2 defines the RSR (Reserved) lines as may be ground or may be open, but they are still passed through the cable. Most present standard SCSI devices will ground those lines. -------------------- microSCSI to SCSI Diagram ---------------------- ----- SCSI Connector Pinouts (single-ended) ------------------------------------ -------------------------------- ----- | SCSI | | MINI | | | SCSI | | MINI | | | SIGNAL| DD-50P | MICRO | DD-50SA | | SIGNAL | DD-50P | MICRO | DD- 50SA | ------------------------------------ -------------------------------- ----- | -DB(0)| 2 | 26 | 34 | | GND | 1 | 1 | 1 | | -DB(1)| 4 | 27 | 2 | | GND | 3 | 2 | 18 | | -DB(2)| 6 | 28 | 19 | | GND | 5 | 3 | 35 | | -DB(3)| 8 | 29 | 36 | | GND | 7 | 4 | 3 | | -DB(4)| 10 | 30 | 4 | | GND | 9 | 5 | 20 | | -DB(5)| 12 | 31 | 21 | | GND | 11 | 6 | 37 | | -DB(6)| 14 | 32 | 38 | | GND | 13 | 7 | 5 | | -DB(7)| 16 | 33 | 6 | | GND | 15 | 8 | 22 | | -DB(P)| 18 | 34 | 23 | | GND | 17 | 9 | 39 | | GND | 20 | 35 | 40 | | GND | 19 | 10 | 7 | | GND | 22 | 36 | 8 | | GND | 21 | 11 | 24 | | RSR | 24 | 37 | 25 | | RSR | 23 | 12 | 41 | |TERMPWR| 26 | 38 | 42 | | OPEN | 25 | 13 | 9 | | RSR | 28 | 39 | 10 | | RSR | 27 | 14 | 26 | | GND | 30 | 40 | 27 | | GND | 29 | 15 | 43 | | -ATN | 32 | 41 | 44 | | GND | 31 | 16 | 11 | | GND | 34 | 42 | 12 | | GND | 33 | 17 | 28 | | BSY | 36 | 43 | 29 | | GND | 35 | 18 | 45 | | -ACK | 38 | 44 | 46 | | GND | 37 | 19 | 13 | | -RST | 40 | 45 | 14 | | GND | 39 | 20 | 30 | | -MSG | 42 | 46 | 31 | | GND | 41 | 21 | 47 | | -SEL | 44 | 47 | 48 | | GND | 43 | 22 | 15 | | -C/D | 46 | 48 | 16 | | GND | 45 | 23 | 32 | | -REQ | 48 | 49 | 33 | | GND | 47 | 24 | 49 | | -I/O | 50 | 50 | 50 | | GND | 49 | 25 | 17 | ------------------------------------ -------------------------------- ----- * NC = NOT CONNECTED CONNECTOR TYPES: DD-50SA ________________________ MINI-MICRO DD-50P | ------------------- | ______________________ ______ ______ |17 \. . . . . . . . . /1 | | _________________ | 49| . . . . . .| 1 |33 \. . . . . . . . /18 | | 1\ - - - - - - - /25 | 50| . . . . . .|2 |50 \. . . . . . . / 34 | | 26\- - - - - - -/50 | ------------- | ------------- | | ----------- -- | ------------------------- --------------- ------- ribbon cable Old style Sun SCSI "SCSI-2" male male __________________ ( 1 25 ) \ ++++++++++++++ / \ 26 50/ -------------- "Centronics" 50 male (use pin numbers for MINI-MICRO) (VIEWED FROM FACE OF CONNECTOR - USE VENDOR NUMBERING SYSTEM AS SPECIFIED) 16 bit Wide SCSI-3 "P" (Primary) Connector pinout (single-ended) -------------------- -------------------- | SCSI | HIGH DEN | | SCSI | HIGH DEN | | SIGNAL | 68 PIN | | SIGNAL | 68 PIN | -------------------- -------------------- | GND | 1 | | -DB(12)| 35 | | GND | 2 | | -DB(13)| 36 | | GND | 3 | | -DB(14)| 37 | | GND | 4 | | -DB(15)| 38 | | GND | 5 | | -DB(P1)| 39 | | GND | 6 | | -DB(0) | 40 | | GND | 7 | | -DB(1) | 41 | | GND | 8 | | -DB(2) | 42 | | GND | 9 | | -DB(3) | 43 | | GND | 10 | | -DB(4) | 44 | | GND | 11 | | -DB(5) | 45 | | GND | 12 | | -DB(6) | 46 | | GND | 13 | | -DB(7) | 47 | | GND | 14 | | -DB(P) | 48 | | GND | 15 | | GND | 49 | | GND | 16 | | GND | 50 | |TERMPWR | 17 | |TERMPWR | 51 | |TERMPWR | 18 | |TERMPWR | 52 | | RSRVD | 19 | | RSRVD | 53 | | GND | 20 | | GND | 54 | | GND | 21 | | -ATN | 55 | | GND | 22 | | GND | 56 | | GND | 23 | | BSY | 57 | | GND | 24 | | -ACK | 58 | | GND | 25 | | -RST | 59 | | GND | 26 | | -MSG | 60 | | GND | 27 | | -SEL | 61 | | GND | 28 | | -C/D | 62 | | GND | 29 | | -REQ | 63 | | GND | 30 | | -I/O | 64 | | GND | 31 | | -DB(8) | 65 | | GND | 32 | | -DB(9) | 66 | | GND | 33 | | -DB(10)| 67 | | GND | 34 | | -DB(11)| 68 | --------------------- --------------------- ____________________________ | _______________________ | | 1\ - - - - - - - - - - /34 | | 35\- - - - - - - - - -/68 | | ------------------- | ---------------------------- "WIDE SCSI-3 P" male --------------------------------------------------------------------- ------ IBM's "Not really SCSI" connectors: [Editor(GF)] Note that this connector is NON-COMPLIANT WITH ANY SCSI STANDARD! 60 pin Burndy connector as used on IBM RS/6000 systems: Pin Signal Pin Signal --- ------ --- ----- 1 Gnd 31 Gnd 2 -DB(0) 32 -ATN 3 Gnd 33 Gnd 4 -DB(1) 34 Gnd 5 Gnd 35 Gnd 6 -DB(2) 36 -BSY 7 Gnd 37 Gnd 8 -DB(3) 38 -ACK 9 Gnd 39 Gnd 10 -DB(4) 40 -RST 11 Gnd 41 Gnd 12 -DB(5) 42 -MSG 13 Gnd 43 Gnd 14 -DB(6) 44 -SEL 15 Gnd 45 Gnd 16 -DB(7) 46 -C/D 17 Gnd 47 Gnd 18 -DB(P) 48 -REQ 19 Gnd 49 Gnd 20 Gnd 50 -I/O 21 Gnd 51 Gnd 22 Gnd 52 Reserved 23 Gnd 53 Reserved 24 Gnd 54 Reserved 25 N/C 55 Reserved 26 TERMPWR 56 Reserved 27 Gnd 57 Reserved 28 Gnd 58 Reserved 29 Gnd 59 Reserved 30 Gnd 60 Reserved Table of Contents ==== ANSWER From: Gary Field (gfield@zk3.dec.com) Macintosh Plus SCSI Connector Pinouts Note that this connector is NON COMPLIANT WITH ANY SCSI STANDARD! The grounding is insufficient and does not allow for proper twisted- pair transmission line implementation. It is recommended that a short adapter cable be used to convert to the more common Centronics style 50 pin connection, rather than extend the 25 pin connection any further than necessary. The Macintosh Plus used a NCR 5380 SCSI chip controlled by the MC68000 processor. ___________________ | SCSI DB-25S | | SIGNAL pin(s) | +------------------+ DB-25S (female) | -DB(0) | 8 | _____________________________ | -DB(1) | 21 | 13\ o o o o o o o o o o o o o /1 | -DB(2) | 22 | 25\ o o o o o o o o o o o o /14 | -DB(3) | 10 | ------------------------ | -DB(4) | 23 | View from rear of computer. | -DB(5) | 11 | | -DB(6) | 12 | | -DB(7) | 13 | | -DB(P) | 20 | | GND | 7,9,14 | | GND |16,18,24 | | -ATN | 17 | | BSY | 6 | | -ACK | 5 | | -RST | 4 | | -MSG | 2 | | -SEL | 19 | | -C/D | 15 | | -REQ | 1 | | -I/O | 3 | +------------------+ Pin 25 is NOT CONNECTED in the Mac Plus implementation. Newer Macs connect TERMPWR to pin 25, but are otherwise the same. Future Domain 25 pin connector pinout Used on TMC-830/845 and TMC-850/860/885. Note: Use the Macintosh pinout above for TMC-850M, TMC-1610M, TMC-1650/1670 or MCS-600 ___________________ | SCSI | DB-25S | | SIGNAL| pin(s) | +-----------------+ DB-25S (female) | -DB(0)| 14 | _____________________________ | -DB(1)| 2 | 13\ o o o o o o o o o o o o o /1 | -DB(2)| 15 | 25\ o o o o o o o o o o o o /14 | -DB(3)| 3 | ------------------------ | -DB(4)| 16 | View from rear of computer. | -DB(5)| 4 | | -DB(6)| 17 | | -DB(7)| 5 | | -DB(P)| 18 | | GND |1,6,8,13 | | GND |13,19,25 | | -ATN | 20 | | BSY | 23 | | -ACK | 22 | | -RST | 10 | | -MSG | 21 | | -SEL | 7 | | -C/D | 11 | | -REQ | 24 | | -I/O | 12 | +-----------------+ Pin 9 is NOT CONNECTED Table of Contents ==== QUESTION: What is the difference between SCSI-1 and SCSI-2? ANSWER From Dal Allen: ==== SCSI-1_versus_SCSI-2 In 1985, when the first SCSI standard was being finalized as an American National Standard, the X3T9.2 Task Group was approached by a group of manufacturers. The group wanted to increase the mandatory requirements of SCSI and to define further features for direct-access devices. Rather than delay the SCSI standard, X3T9.2 formed an ad hoc group to develop a working paper that was eventually called the Common Command Set (CCS). Many products were designed to this working paper. In parallel with the development of the CCS working paper, X3T9.2 sought permission to begin working on an enhanced SCSI standard, to be called SCSI-2. SCSI-2 would include the results of the CCS working paper, caching commands, performance enhancement features, and whatever else X3T9.2 deemed worthwhile. While SCSI-2 was to go beyond the original SCSI standard (now referred to as SCSI-1), it was to retain a high degree of compatibility with SCSI-1 devices. How is SCSI-2 different from SCSI-1? 1. Several options were removed from SCSI-1: a. Single initiator option was removed. b. Non-arbitrating Systems option was removed. c. Non-extended sense data option was removed. d. Reservation queuing option was removed. e. The read-only device command set was replaced by the CD-ROM command set. f. The alternative 1 shielded connector was dropped. 2. There are several new low-level requirements in SCSI-2: a. Parity must be implemented. b. Initiators must provide TERMPWR -- Targets may provide TERMPWR. c. The arbitration delay was extended to 2.4 us from 2.2 us. d. Message support is now required. 3. Many options significantly enhancing SCSI were added: a. Wide SCSI (up to 32 bits wide using a second cable) b. Fast SCSI (synchronous data transfers of up to 10 Mega-transfers per second -- up to 40 MegaBytes per second when combined with wide SCSI) c. Command queuing (up to 256 commands per initiator on each logical unit) d. High-density connector alternatives were added for both shielded and non- shielded connectors. e. Improved termination for single-ended buses (Alternative 2) f. Asynchronous event notification g. Extended contingent allegiance h. Terminate I/O Process messaging for time-critical process termination. 4. New command sets were added to SCSI-2 including: a. CD-ROM (replaces read-only devices) b. Scanner devices c. Optical memory devices (provides for write-once, read-only, and erasable media) d. Medium changer devices e. Communications devices 5. All command sets were enhanced: a. Device Models were added b. Extended sense was expanded to add: + Additional sense codes + Additional sense code qualifiers + Field replaceable unit code + Sense key specific bytes c. INQUIRY DATA was expanded to add: + An implemented options byte + Vendor identification field + Product identification field + Product revision level field + Vital product data (more extensive product reporting) d. The MODE SELECT and MODE SENSE commands were paged for all device types e. The following commands were added for all device types: + CHANGE DEFINITION + LOG SELECT + LOG SENSE + READ BUFFER + WRITE BUFFER f. The COPY command definition was expanded to include information on how to handle inexact block sizes and to include an image copy option. g. The direct-access device command set was enhanced as follows: + The FORMAT UNIT command provides more control over defect management + Cache management was added: - LOCK/UNLOCK CACHE command - PREFETCH command - SYNCHRONIZE CACHE command - Force unit access bit - Disable page out bit + Several new commands were added: - READ DEFECT DATA - READ LONG - WRITE LONG - WRITE SAME + The sequential-access device command set was enhanced as follows: - Partitioned media concept was added: * LOCATE command * READ POSITION command - Several mode pages were added - Buffered mode 2 was added - An immediate bit was added to the WRITE FILEMARKS command + The printer device command set was enhanced as follows: - Several mode pages defined: * Disconnect/reconnect * Parallel printer * Serial printer * Printer options + The write-once (optical) device command set was enhanced by: - Several new commands were added: * MEDIUM SCAN * READ UPDATED BLOCK * UPDATE BLOCK - Twelve-byte command descriptor blocks were defined for several commands to accommodate larger transfer lengths. ======================================================= The following article was written by Dal Allan of ENDL in April 1990. It was published nine months later in the January 1991 issue of "Computer Technology Review". While it appeared in the Tape Storage Technology Section of CTR, the article is general in nature and tape- specific. In spite of the less than timely publication, most of the information is still valid. It is reprinted here with the permission of the author. If you copy this article, please include this notice giving "Computer Technology Review" credit for first publication. What's New in SCSI-2 Scuzzy is the pronunciation and SCSI (Small Computer System Interface) is the acronym, for the best known and most widely used ANSI (American National Standards Institute) interface. Despite use of the term "Small" in its name, everyone has to agree that Scuzzy is large - in use, in market impact, in influence, and unfortunately, in documentation. The standards effort that began with a 20-page specification in 1980 has grown to a 600 page extravaganza of technical information. Even before ANSI (American National Standards Institute) published the first run of SCSI as a standards document in 1986, ASC (Accredited Standards Committee) X3T9.2 was hard at work on SCSI-2. No technical rationale can be offered as to why SCSI-1 ended and SCSI-2 began, or as to why SCSI-2 ended and SCSI-3 began. The justification is much more simple - you have to stop sometime and get a standard printed. Popular interfaces never stop evolving, adapting, and expanding to meet more uses than originally envisaged. Interfaces even live far beyond their technological lifespan. SMD (Storage Module Drive) has been called technically obsolete for 5 years but every year there are more megabytes shipped on the SMD interface than the year before. This will probably continue for another year or so before the high point is reached, and it will at least a decade before SMD is considered to be insignificant. If SCSI enhancements are cut off at an arbitrary point, what initiates the decision? Impatience is as good an answer as any. The committee and the market get sick of promises that the revision process will "end soon," and assert pressure to "do it now." The SCSI-3 effort is actively under way right now, and the workload of the committee seems to be no less than it was a year ago. What is pleasant, is that the political pressures have eased. There is a major difference between the standards for SCSI in 1986 and SCSI-2 in 1990. The stated goal of compatibility between manufacturers had not been achieved in SCSI in 1986 due to a proliferation of undocumented "features." Each implementation was different enough that new software drivers had to be written for each device. OEMs defined variations in hardware that required custom development programs and unique microcode. Out of this diversity arose a cry for commonality that turned into CCS (Common Command Set), and became so popular that it took on an identity of its own. CCS defined the data structures of Mode Select and Mode Sense commands, defect management on the Format command, and error recovery procedures. CCS succeeded because the goals were limited, the objectives clear and the time was right. CCS was the beginning of SCSI-2, but it was only for disks. Tape and optical disks suffered from diversity, and so it was that the first working group efforts on SCSI-2 were focused on tapes and optical disks. However, opening up a new standards effort is like lifting the lid on Pandora's Box - it's hard to stay focused on a single task. SCSI-2 went far beyond extending and consolidating CCS for multiple device types. SCSI-2 represents three years of creative thought by some of the best minds in the business. Many of the new features will be useful only in advanced systems; a few will find their way into the average user's system. Some may never appear in any useful form and will atrophy, as did some original SCSI features like Extended Identify. Before beginning coverage of "what's new in SCSI-2," it might be well to list some of the things that aren't new. The silicon chips designed for SCSI are still usable. No new features were introduced which obsolete chips. The cause of silicon obsolescence has been rapid market shifts in integrating functions to provide higher performance. Similarly, initiators which were designed properly, according to SCSI in 1986, will successfully support SCSI-2 peripherals. However, it should be pointed out that not all the initiators sold over the last few years behaved according to the standard, and they can be "blown away "by SCSI-2 targets. The 1986 standard allows either initiators or targets to begin negotiation for synchronous transfers, and requires that both initiators and targets properly handle the sequence. A surprisingly large percentage of SCSI initiators will fail if the target begins negotiation. This has not been as much of a problem to date as it will become in the future, and you know as well as I do, that these non-compliant initiators are going to blame the SCSI-2 targets for being "incompatible." Quirks in the 1986 standard, like 4 bytes being transferred on Request Sense, even if the requested length was zero have been corrected in SCSI-2. Initiators which relied on this quirk instead of requesting 4 bytes will get into trouble with a SCSI-2 target. A sincere effort has been made to ensure that a 1986-compliant initiator does not fail or have problems with a SCSI-2 target. If problems occur, look for a non-compliant initiator before you blame the SCSI-2 standard. After that little lecture, let us turn to the features you will find in SCSI-2 which include: o Wide SCSI: SCSI may now transfer data at bus widths of 16 and 32 bits. Commands, status, messages and arbitration are still 8 bits, and the B-Cable has 68 pins for data bits. Cabling was a confusing issue in the closing days of SCSI-2, because the first project of SCSI-3 was the definition of a 16-bit wide P-Cable which supported 16-bit arbitration as well as 16-bit data transfers. Although SCSI-2 does not contain a definition of the P-Cable, it is quite possible that within the year, the P-Cable will be most popular non-SCSI-2 feature on SCSI-2 products. The market responds to what it wants, not the arbitrary cutoffs of standards committees. o Fast SCSI: A 10 MHz transfer rate for SCSI came out of a joint effort with the IPI (Intelligent Peripheral Interface) committee in ASC X3T9.3. Fast SCSI achieves 10 Megabytes/second on the A-Cable and with wider data paths of 16- and 32-bits can rise to 20 Megabytes/second and even 40 Megabytes/second. However, by the time the market starts demanding 40 Megabytes/second it is likely that the effort to serialize the physical interface for SCSI-3 will attract high- performance SCSI users to the Fiber Channel. A word of caution. At this time the fast parameters cannot be met by the Single Ended electrical class, and is only suitable for Differential. One of the goals in SCSI-3 is to identify the improvements needed to achieve 10 MHz operation with Single Ended components. o Termination: The Single Ended electrical class depends on very tight termination tolerances, but the passive 132 ohm termination defined in 1986 is mismatched with the cable impedance (typically below 100 ohms). Although not a problem at low speeds when only a few devices are connected, reflections can cause errors when transfer rates increase and/or more devices are added. In SCSI-2, an active terminator has been defined which lowers termination to 110 ohms and is a major boost to system integrity. o Bus Arbitration, Parity and the Identify Message were options of SCSI, but are required in SCSI-2. All but the earliest and most primitive SCSI implementations had these features anyway, so SCSI-2 only legitimizes the de facto market choices. The Identify message has been enhanced to allow the target to execute processes, so that commands can be issued to the target and not just the LUNs. o Connectors: The tab and receptacle microconnectors chosen for SCSI- 2 are available from several sources. A smaller connector was seen as essential for the shrinking form factor of disk drives and other peripherals. This selection was one of the most argued over and contentious decisions made during SCSI-2 development. o Rotational Position Locking: A rose by any other name, this feature defines synchronized spindles, so than an initiator can manage disk targets which have their spindles locked in a known relative position to each other. Synchronized disks do not all have to be at Index, they can be set to an offset in time relative to the master drive. By arraying banks of synchronized disks, faster transfer rates can be achieved. o Contingent Allegiance: This existed in SCSI-1, even though it was not defined, and is required to prevent the corruption of error sense data. Targets in the Contingent Allegiance state reject all commands from other initiators until the error status is cleared by the initiator that received the Check Condition when the error occurred. Deferred errors were a problem in the original SCSI but were not described. A deferred error occurs in buffered systems when the target advises Good Status when it accepts written data into a buffer. Some time later, if anything goes wrong when the buffer contents are being written to the media, you have a deferred error. o Extended Contingent Allegiance (ECA): This extends the utility of the Contingent Allegiance state for an indefinite period during which the initiator that received the error can perform advanced recovery algorithms. o Asynchronous Event Notification (AEN): This function compensates for a deficiency in the original SCSI which did not permit a target to advise the initiator of asynchronous events such as a cartridge being loaded into a tape drive. o Mandatory Messages: The list of mandated messages has grown: +----------------------+--------------------------+------------------ -+ | Both | Target | Initiator | +----------------------+--------------------------+------------------ -| | Identify | Abort | Disconnect | | | | | | Message Reject | No Operation | Restore Pointer | | | | | | Message Parity Error | Bus Device Reset | Save Data Pointer | | | | | | | Initiator Detected Error | | +----------------------+--------------------------+------------------ -+ o Optional messages have been added to negotiate wide transfers and Tags to support command queueing. A last-minute inclusion in SCSI-2 was the ability to Terminate I/O and receive the residue information in Check Condition status (so that only the incomplete part of the command need be re-started by the initiator). o Command Queueing: In SCSI-1, initiators were limited to one command per LUN e.g. a disk drive. Now up to 256 commands can be outstanding to one LUN. The target is allowed to re-sequence the order of command execution to optimize seek motions. Queued commands require Tag messages which follow the Identify. o Disk Cacheing: Two control bits are used in the CDB (Command descriptor Block) to control whether the cache is accessed on a Read or Write command, and some commands have been added to control pre- fetching and locking of data into the cache. Users do not have to change their software to take advantage of cacheing, however, as the Mode Select/Mode Sense Cache page allows parameters to be set which optimize the algorithms used in the target to maximize cache performance. Here is another area in which improvements have already been proposed in SCSI-3, and will turn up in SCSI-2 products shipping later this year. o Sense Keys and Sense Codes have been formalized and extended. A subscript byte to the Sense Code has been added to provide specifics on the type of error being reported. Although of little value to error recovery, the additional information about error causes is useful to the engineer who has to analyze failures in the field, and can be used by host systems as input to prognostic analysis to anticipate fault conditions. o Commands: Many old commands have been reworked and several new commands have been added. o Pages: Some method had to be found to pass parameters between host and target, and the technique used is known as pages. The concept was introduced in CCS and has been expanded mightily in SCSI-2. A number of new Common Commands have been added, and the opcode space for 10-byte CDBs has been doubled. o Change Definition allows a SCSI-2 initiator to instruct a SCSI-2 target to stop executing according to the 1986 standard, and provide advanced SCSI-2 features. Most SCSI-2 targets will power on and operate according to the 1986 standard (so that there is no risk of "disturbing" the installed initiators), and will only begin operating in SCSI-2 mode, offering access to the advanced SCSI-2 capabilities, after being instructed to do so by the initiator using the Change Definition command. o The Mode Select and Mode Sense pages which describe parameters for operation have been greatly expanded, from practically nothing in 1986 to hundreds of items in SCSI-2. Whenever you hear of something being described as powerful and flexible tool, think complicated. Integrators are advised to be judicious in their selection of the pages they decide to support. o The Inquiry command now provides all sorts of interesting data about the target and its LUNs. Some of this is fixed by the standard, but the main benefit may be in the Vendor Unique data segregated into the special designation of Vital Product Data, which can be used by integrators as a tool to manage the system environment. o Select Log and Sense Log have been added so that the initiator can gather both historical (e.g. all Check Conditions) and statistical (e.g. number of soft errors requiring ECC) data from the target. o Diagnostic capabilities have been extended on the Read/Write Buffer and Read/Write Long commands. The ways in which the target can manage bad blocks in the user data space have been defined further and regulated to reduce inconsistencies in the 1986 standard. A companion capability to Read Defect Data permits the initiator to use a standard method to be advised of drive defect lists. o A new group of 12-byte command blocks has been defined for all optical devices to support the large volume sizes and potentially large transfer lengths. The Erase command has been added for rewritable optical disks so that areas on the media can be pre-erased for subsequent recording. Write Once disks need Media Scan, so that the user can find blank areas on the media. o New command sets have been added for Scanners, Medium Changers, and CDROMs. All of this technical detail can get boring, so how about some "goodies" in SCSI-2 which benefit the common man and help the struggling engineer? First, and probably the best feature in SCSI-2 is that the document has been alphabetized. No longer do you have to embark on a hunt for the Read command because you cannot remember the opcode. In the 1986 standard, everything was in numeric sequence, and the only engineers who could find things easily were the microprogrammers who had memorized all the message and opcode tables. Now, ordinary people can find the Read command because it is in alphabetic sequence. This reorganization may sound like a small matter but it wasn't, it required a considerable amount of effort on the part of the SCSI-2 editors. It was well worth it. Another boon is the introduction for each device class of models which describe the device class characteristics. The tape model was the most needed, because various tape devices use the same acronym but with different meanings or different acronyms for the same meaning. The SCSI-2 tape model defines the terms used by SCSI-2, and how they correspond to the acronyms of the different tapes. For example, on a 9-track reel, End of Tape is a warning, and there is sufficient media beyond the reflective spot to record more data and a trailer. Not so on a 1/4" tape cartridge. End of Tape means out of media and no more data can be written. This sort of difference in terms causes nightmares for standardization efforts. So there it is; a summary of what is in SCSI-2. It's not scary, although it is daunting to imagine plowing through a 600-page document. Time for a commercial here. The "SCSI Bench Reference" available from ENDL Publications (408-867-6642), is a compaction of the standard. It takes the 10% of SCSI-2 which is constantly referenced by any implementor, and puts it in an easy-to-use reference format in a small handbook. The author is Jeff Stai, one of the earliest engineers to become involved with SCSI implementation, and a significant contributor to the development of both the 1986 standard and SCSI-2. SCSI-2 is not yet published as a standard, but it will be available later this year. Until then, the latest revision can be purchased from Global Engineering (800-854-7179). Biography Consultant and analyst I. Dal Allan is the founder of ENDL and publisher of the ENDL Letter and the "SCSI Bench Reference." A pioneer and activist in the development and use of standard interfaces, he is Vice Chairman of ASC X3T9.2 (SCSI) and Chairman of the SCSI-2 Common Access Method Committee. Table of Contents ==== QUESTION: What is the difference between SCSI-2 and SCSI-3? ANSWER From: excerpts of postings by Jeff Stai and others: (Mohit K Goyall - goyall@utdallas.edu), (Andrew E. Lowman - lowman@arizona.edu) ==== Are SCSI-3 hard drives and/or controllers available yet? Allegedly, Previous postings have said "I heard that SCSI-3 has been standardized," but I haven't seen anything firm about it. I've seen controllers advertised by JDR Microdevices and some cheap clones; the Quantum "Empire" drives are also advertised as SCSI-3 by some mail order vendors. Seagate and IBM call their fastest drives (probably comparable in speed to the Quantums, if not faster) "Wide SCSI-2." That's a misnomer. See below. What is the difference between SCSI-3 and Fast & Wide SCSI-2? Wide SCSI-2 required two cables to do 16 bit wide transfers. SCSI-3 defined a single cable, single REQ/ACK 16 bit, WIDE transfer. The reason you are hearing 16-bit single cable being called SCSI-3 is that they CAN. The fact that single cable 16-bit has been around for a while just shows you how much the standardization process lags behind the real world. SCSI-3 is really a family of standards. SCSI was broken up from a single document into different layers and command sets. This was done to allow for different physical transport layers (like fibre channel and SSA) to be defined, and to allow for smaller "bite-sized" projects that maybe get done a little faster ;-) The family includes the following members with TLAs: - SCSI-3 Parallel Interface (SPI): Defines the mechanical, timing, phases, and electrical parameters of the parallel cable we all know and love. Some of the electrical and cable parameters are tightened/improved over SCSI-2. - SCSI-3 Interlock Protocol (SIP): Defines the messages and how the phases are invoked. No real change from SCSI-2, except for some new messages. - SCSI-3 Architectural Model (SAM): In a nutshell, defines a common set of functions and services and definitions for how a physical transport properly gets commands, data, and status exchanged between two devices, complete with error handling and queueing. - SCSI-3 Primary Commands (SPC): All of the commands executed by any and all SCSI devices, like REQUEST SENSE and INQUIRY, etc. - SCSI-3 Block Commands (SBC): Disk commands. - SCSI-3 Stream Commands (SBC): Tape commands. - SCSI-3 Controller Commands (SCC): RAID box commands. - SCSI-3 Multimedia Commands (MMC): For CDROMS etc. - SCSI-3 Fibre Channel Protocol (FCP): SCSI commands over gigabit Fibre Channel. - SCSI-3 Serial Bus Protocol (SBP): SCSI commands over IEEE 1394 High Speed Serial Bus (Apple's "Firewire"). - SCSI-3 Serial Storage Protocol (SSP): SCSI commands over SSA. whew. Q: After perusing the latest issue of Computer Shopper, I came away with the impression that companies are calling F&W SCSI-2 HD's SCSI- 3. Is this an incorrect assumption, or is F&W SCSI-2 known as SCSI-3? Is this really mostly marketing hype? Actually, there is something to that. TECHNICALLY, what is out there is often a hybrid: SCSI-3 "SPI" silicon with some other hodgepodge of SCSI-3 proposals, all mixed in with SCSI-2 stuff. An earlier posting said that the Quantum Empire ("SCSI-3") drives contain some commands from the SCSI-3 command set, and Adaptec suggested a specific setting on its 2940W controller to work properly with the drive. I understand there are some drives with proposed SCSI-3 command features. These are mostly in the MODE SELECT and in error codes, as I recall. Perhaps someone who knows more about this could elaborate? Note also that the major players (like DC Drives) don't have any "SCSI-3" stuff advertised; only JDR and some cheap clones are promoting it. Besides, Wide SCSI-2 has yet to really catch on (mostly because only a few drives are fast enough to take advantage of it). There is no "wide SCSI-2" because that would mean two cables. Single cable wide SCSI has always been SCSI-3, it just took too d*** long to get into a standard! :-) Table of Contents ==== QUESTION: Is SYNCHRONOUS faster than ASYNCHRONOUS? ANSWER From: Gary Field (gfield@zk3.dec.com ) ==== Yes, the asynchronous transfer option waits for each byte to be transferred before it is acknowledged. With synchronous protocol, the device sending the data is allowed to get ahead of the device receiving the data by a number of bytes (called the offset). The offset is negotiated between the initiator and the target some time prior to the transfer beginning. The synchronous protocol is considerably more efficient and therefore faster than asynchronous. See also: 1, 2, 3 Table of Contents ==== QUESTION: Is the NCR 53C90 Faster than spec? ANSWER From: kstewart@ncr-mpd.FtCollins.NCR.COM (Ken Stewart) ==== I've seen a few comments about our 54C90 being faster than spec. While I doubt the author was really complaining (I got twice as much as I paid for - sure makes me mad ;) I'd like to explain the situation. Along the way, I'll also show that asynchronous is faster on short cables, while synchronous is faster on long cables. The cross-over point occurs somewhere around six feet--assuming that you have our 53C90 family devices at both ends of the cable. The reason has to do with the propagation delay of the cable; the turn around time of the silicon; and the interlocked nature of the asynchronous handshake. 1) We have measured propagation delays from various cables and found an average of 1.7 nanoseconds per foot, which is roughly 5.25 ns per meter. 2) The turn-around time is the amount of time the SCSI chip takes to change an output in response to an input. If REQ is an input then ACK is an output. Or if ACK is an input then REQ is an output. Typical turn-around time for the 53C90 is 40 nanoseconds. 3) The asynchronous transfer uses an interlocked handshake where a device cannot do the next thing until it receives positive acknowledgment that the other device received the last thing. First REQ goes true /* driven by Target */ then ACK is permitted to go true /* driven by Initiator */ then REQ is permitted to go false then ACK is permitted to go false Thus we have four "edges" propagating down the cable plus 4 turn- around delays. Asynchronous transfer requires 55 ns setup and no hold time (paragraph in in SCSI-1 or SCSI-2) which gives an upper speed limit around 18 MB/s. A detailed analysis (assuming 53C90 family) shows that the setup time subtracts out. This is mostly because we are running at one-third the max rate, but also because setup for the next byte can begin anytime after ACK is received true or REQ is received false, depending on who is receiving. You can either take my word for it or draw the waveforms yourself. Thus, the asynchronous transfer reduces to: (4 * 1.7 * 1) + (4 * 40ns) = 167 ns /* 1 foot cable */ = 6 MB/s (4 * 5.25 * 6) + (4 * 40ns) = 286 ns /* 6 meter cable */ = 3.5 MB/s (4 * 5.25 * 25) + (4 * 40ns) = 685 ns /* 25 meter cable */ = 1.5 MB/s note: cables longer than 6 meters require external differential transceivers which add delay and degrade the performance even more than indicated here. Our simulations say that under very best conditions (fast silicon, low temperature, high voltage, zero length cable) we can expect more than 8 MB/s asynchronously. In the lab, I routinely measure 5 MB/s on 8 foot cables. So, if you were writing the data manual for this, how would YOU spec it? The framers of the SCSI spec threw in synchronous mode to boost the performance on long cables. In synchronous mode, the sending device is permitted to send the next byte without receiving acknowledgment that the receiver actually received the last byte. Kind of a ship and pray method. The acknowledgment is required to come back sometime, but we just don't have to wait for it (handwave the offset stuff and the ending boundary conditions). In this mode any external transceivers add a time shift, but not a delay. So if you negotiate for 5 MB/s, you get 5MB/s regardless how long the cable is and regardless whether you are single-ended or differential. But you can't go faster than 5.5 MB/s, except in SCSI-2. Synchronous mode does have a hold time (unlike asynch) but again, setup and hold times subtract out. In SCSI-1 synchronous mode, the speed limit comes from the combined ASSERTION PERIOD + NEGATION PERIOD which is 90ns + 90ns = 180ns = 5.5 MB/s. Our 53C90 family doesn't quite hit the max, but we do guarentee 5.0 MB/s. In SCSI-2, anything above 5.0 MB/s is considered to be FAST. Here the maximum transfer rate is explicitly limited to 100 ns or 10MB/s; you don't have to read between the lines to deduce it. Interesting tid-bit: given a SCSI-2 FAST period of 100 ns and a cable delay of 131 ns on a 25 meter cable, you can actually stack 1.31 bytes in the 8-bit cable. In FAST and WIDE SCSI you can stack 5.24 bytes in this copper FIFO. Hummm... Table of Contents ==== QUESTION: What are the jumpers on my Conner drive? ANSWER From: ekrieger@quasar.hacktic.nl (Eric Krieger) Embellishment from: Henrik Stahl (f92-hst@nada.kth.se) ==== QUICK INSTALLATION GUIDE SCSI Most SCSI host adapters are compatible with Conner drives. Software drivers and installation instructions are provided with the host adapter. The drives are shipped with SCSI ID set to 7. To select a different ID refer to the following: Table A Table B ID E-1 E-2 E-3 ID E2 E3 E4 0 out out out 0 out out out 1 in out out 1 in out out 2 out in out 2 out in out 3 in in out 3 in in out 4 out out in 4 out out in 5 in out in 5 in out in 6 out in in 6 out in in 7 in in in 7 in in in Parity is always ENABLED on the CP3200,CP30060,CP30080,CP30100, CP 30200, CP 3500, CP 3360, CP 30540 and CP 31370. For the CP 340, jumper E-1 to disable parity. All other models, jumper E-4 to disable parity. SCSI drive parameters: Model Hds Cyl Sec Table LED CP2020 2 642 32 A n/a CP340 4 788 26 B 1 CP3020 2 622 33 A 1 CP3040 2 1026 40 A 1 CP3180 6 832 33 A 1 CP3100 8 776 33 A 1 CP30060 2 1524 39 A 2 CP30080 4 1053 39 A 2 CP30100 4 1522 39 A 2 CP30200 4 2119 49 A 2 CP3200 8 1366 38 A 2 CP3360 8 1806 49 A 2 CP3540 12 1806 49 A 2 CP 30080E 2 1806 46 AA C/E CP 30170E 4 1806 46 AA C/E CP 30540 6 2249 59-89 AA B CP 31370 14 2094 59-95 AA B LED 1 LED 2 J-4 Pin 1 = + J-1 Pin 3 = + Pin 2 = - Pin 4 = - On the CP 31370, jumper E5 enables termination. Default is termination on. It may be the same jumper for other models. Table of Contents ==== QUESTION: What are the jumpers for my Wangtek 5150 drive? ANSWER From: Terry Kennedy (terry@spcvxa.spc.edu) ==== First, the disclaimer: This is not an official representation of Wangtek or of my employer. This is info I've discovered by reading publicly available reference material. When changing jumpers, always observe proper anti-static precautions and be sure you have the current configuration written down so you have a known starting point. Ok. Here's the complete scoop on Wangtek 5150ES drives: The current part number for a "generic" 5150ES is: 33685-201 (black faceplate) 33685-202 (beige faceplate) These are referred to as the "ACA version" of the drive. There are _many_ other part numbers for 5150ES drives. If you have one that isn't one of the above, it doesn't mean you have an old or an out of rev drive, it just means it's a special version created for a distributor or OEM, or with different default jumper settings. You can order the Wangtek 5150ES OEM Manual from Wangtek. It is part number 63045-001 Revision D. There are 5 possible logic boards. Here are the jumper options for each: Logic assembly #33678 --------------------- (J10) 0 - SCSI unit LSB 1 - SCSI unit 2 - SCSI unit MSB K - not documented J32 - Diagnostic test connector, default is not installed E1, F1 - SCSI termination power. E1 in = power from drive and to cable, E1 out - power from cable. F1 = terminator power fuse, 1.5A FB. Default is IN. E2 - Chassis ground. E2 in jumpers logic to chassis ground. E2 out isolates through a .33 uFD capacitor. Default is IN. E5 - Master oscillator enable. Test only. Must be IN. E20 - Factory test. Must be OUT. RP1, RP2, RP3 - SIP terminators. Default is IN, remove for no termination. Logic assembly #30559 --------------------- HDR1 - Factory testing. Setting depends on drive. Don't touch. HDR2 - Factory testing. Defaults are pins 15-16, 17-18, 19-20. Don't touch. HDR3 pin 1 - A-B enables buffered mode. B-C disables. Can be overridden by SCSI Mode Select. HDR3 pin 2, 3 - Default data format. Set to B-C for a 5150ES. HDR3 pin 4 - parity enable. A-B enables, B-C disables. (J10) 0 - SCSI unit LSB 1 - SCSI unit 2 - SCSI unit MSB K - not documented E1 - SCSI termination power. E1 in = power from drive and to cable, E1 out - power from cable. E2 - Chassis ground. E2 in jumpers logic to chassis ground. E2 out isolates through a .33 uFD capacitor. Default is IN. E3 - Master oscillator enable. Test only. Must be IN. E4 - Write test mode. Test only. Must be OUT. E5 - Write oscillator enable. Test only. Must be IN. E6 - Disable HDR2. Test only. Must be IN. E7 - Microcontroller clock select. In for a 5150ES. E8 - Write precomp select. Set on a per-drive basis. Don't touch. E9 - RAM size. Don't touch. E10 - Erase frequency. Don't touch. RP2, RP3 - DIP and SIP terminators. Default is IN, remove for no termination. Logic assembly #30600 --------------------- HDR1 - Factory testing. Setting depends on drive. Don't touch. HDR2 - Write precomp select. Set on a per-drive basis. Don't touch. HDR3 pin 1, 2, 3 - SCSI device address. 1 is LSB, 3 is MSB. A-B=1, B- C=0 HDR3 pin 4 - Parity enable. IA-B is enabled. HDR3 pin 5, 6 - Default data format. B-C for a 5150ES. HDR3 pin 7 - Buffered mode select. A-B is enabled. HDR3 pin 8 - Reserved. Must be OUT. HDR4 - Write frequency select. Don't touch. E1 - SCSI termination power. E1 in = power from drive and to cable, E1 out - power from cable. E2 - Chassis ground. E2 in jumpers logic to chassis ground. E2 out isolates through a .33 uFD capacitor. Default is IN. E3 - Hard/soft reset. IN enables hard reset. E4 - Write precomp select. Don't touch. E5 - Clock speed. Don't touch. E6 - Tape hole test. Don't touch. Logic assembly #30552 --------------------- HDR1 - Factory testing. Setting depends on drive. Don't touch. HDR2 - Write precomp select. Set on a per-drive basis. Don't touch. HDR3 pin 1, 2, 3 - SCSI device address. 1 is LSB, 3 is MSB. [Note - HDR3 pins 1-3 are duplicated at another location on the board] HDR3 pin 4 - Parity enable. IN is enabled. HDR3 pin 5, 6, 7, 8 - Default data format. 5,5 B-C, 7-8 A-B for a 5150ES. HDR4 - Write frequency select. Don't touch. E1 - SCSI termination power. E1 in = power from drive and to cable, E1 out - power from cable. E2 - Chassis ground. E2 in jumpers logic to chassis ground. E2 out isolates through a .33 uFD capacitor. Default is IN. E3 - Hard/soft reset. IN enables hard reset. E4 - Write precomp select. Don't touch. E5 - Clock speed. Don't touch. E6 - Tape hole test. Don't touch. Logic assembly #30427 --------------------- HDR1 - Factory testing. Setting depends on drive. Don't touch. HDR2 - Write precomp select. Set on a per-drive basis. Don't touch. HDR3 pin 1, 2, 3 - SCSI device address. 1 is LSB, 3 is MSB. A-B=1, B- C=0 HDR3 pin 4 - Parity enable. IA-B is enabled. HDR3 pin 5, 6, 7, 8 - Default data format. 5,5 B-C, 7-8 A-B for a 5150ES. E1, E3 - Factory test. Must be IN. E2 - SCSI termination power. E2 in = power from drive and to cable, E2 out - power from cable. E4 - Chassis ground. E4 in jumpers logic to chassis ground. E4 out isolates through a .33 uFD capacitor. Default is IN. Firmware - There are many flavors of firmware. I have seen the following parts: 24115-xxx 24144-xxx 21158-xxx the -xxx suffix changes as the firmware is updated. According to the folks I spoke to at Wangtek, the standard firmware is the 21158. The latest version as of this writing is 21158-007. All of these will work with the Adaptec and GTAK. The firmware options (as returned by a SCSI Identify) are on the end of the product string, which is "WANGTEK 5150ES SCSI ES41C560 AFD QFA STD" for the 21158-007 firmware. The 3-letter codes have the following meaning: AFD - Automatic Format Detection - the drive will recognize the format (such as QIC-24, QIC-120, or QIC-150) that the tape was written in. QFA - Quick File Access - the ability to rapidly locate a tape block, and to implement the "position to block" and "report block" SCSI commands. This is compatible with the Tandberg implementation. STD - Standard feature set. Table of Contents ==== QUESTION: How do I configure my HP DDS DAT tape drive? ANSWER From: Alan Strassberg (alan@lmsc.lockheed.com) ==== The HP DDS Configuration Guide (postscript) can be found at: http://www.impediment.com/hp/hp_2.ps Table of Contents ==== QUESTION: What is ASPI? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== ASPI stands for Advanced SCSI Programming Interface. It was developed by Adaptec. It is a calling convention and set of commands that can be used to send SCSI commands via any SCSI host adapter that supports it. It is strictly for use with Intel x86 machines running MSDOS, Windows( 3.1x, 95 or NT), Netware, or OS/2. There is no UNIX version. The error reporting and recovery mechanisms are much more limited than in CAM, but ASPI gained much wider acceptance because it was available earlier. Table of Contents ==== QUESTION: What is CAM? ANSWER From: ctjones@bnr.ca (Clifton Jones) ==== CAM stands for Common Access Method. It is an ANSI standard to make it easier to program SCSI applications by encapsulating the SCSI functions into a standardized calling convention. [Editor(GF): It is similar to ASPI but much more elaborate and complete]. ANSWER From: landis@sugs.tware.com (Hale Landis) ==== You can get the CAM spec(s) from the SCSI BBS Table of Contents ==== QUESTION: What is FPT (Termination)? ANSWER From: jvincent@bnr.ca (John Vincent) ==== FPT stands for Forced Perfect Termination. FPT is actually really simple, I wish I had thought of it. What it does is use diode clamps to eliminate over and undershoot. The "trick" is that instead of clamping to +5 and GND they clamp to the output of two regulated voltages. This allows the clamping diodes to turn on earlier and is therefore better at eliminating overshoot and undershoot. The block diagram for a FPTed signal is below. The resistor value is probably in the 110 Ohm range. The actual output voltages of the regulators may not be exaclty as I have shown them but ideally they are matched to the diode characteristics so that conduction occurs when the signal voltage is greater than 3.0 V or less than 0.2 V. +-----------*--- TERMPWR | | ____|___ | | | | | Vreg 1 |---------------------------------* 2.8 V |________| | | | | | ----- | | --- | \ - | / term resistor | \ (110 Ohms) | / ____|___ | | | | | Vreg 2 |-*--------* 2.4 V | |________| | | | | --+-- | | / \ | +------+ /___\ | | | | | | | terminated | *----------*------------- signal | | | | | --+-- | / \ | /___\ Both diodes are fast silicon | | switching diodes (.6 V drop) ___|____ | | | | | Vreg 3 |----------* 0.8 Volts |________| The diagram shows the circuit for terminating one signal. In a complete FPT there would be 36 diodes and 18 110 Ohm resistors plus the regulator chips. Using the values shown, transients would be clamped at 0.2V and 3.0V. [Editor(GF)]: Some errors in the above diagram were corrected as suggested by Wietze van Winden (wietze@ittpub.nl) Table of Contents ==== QUESTION: What is Active Termination? ANSWER From: eric@telebit.com (Eric Smith) and brent@auspex.com (Brent R. Largent) ==== An active terminator actually has one or more voltage regulators to produce the termination voltage, rather than using resistor voltage dividers. This is a passive terminator: TERMPWR ------/\/\/\/------+------/\/\/\/----- GND | | SCSI signal Notice that the termination voltage varies with the voltage on the TERMPWR line. One voltage divider (two resistors) is used for each SCSI signal. An active terminator looks more like this (supply filter caps omitted): 2.85 Volt Regulator +-----------+ +2.85V 110 Ohms TERMPWR -----| in out |------+------/\/\/\/-------SCSI signal | gnd | | +-----------+ | | +------/\/\/\/-------SCSI signal | | GND ---------------+ | +------/\/\/\/-------SCSI signal | etc. Assuming that the TERMPWR voltage doesn't drop below the desired termination voltage (plus the regulator's minimum drop), the SCSI signals will always be terminated to the correct voltage level. Several vendors have started making SCSI active terminator chips, which contain the regulator and the resistors including Dallas Semiconductor, Unitrode Integrated Circuits and Motorola. [Editor(GF): Another nice feature of activer termination is that it can be disabled by a single jumper instead of needing to unplug resistor arrays.] Table of Contents ==== QUESTION: Why Is Active Termination Better? ANSWER brent@auspex.com (Brent R. Largent) ==== Typical passive terminators (resistors) allow signals to fluctuate directly in relation to the TERM Power Voltage. Usually terminating resistors will suffice over short distances, like 2-3 feet, but for longer distances active termination is a real advantage. Active termination provide the following advantages: - Helps reduce noise. - A logic bit can be used to effectively disconnect the termination. - Regulated termination voltage. - SCSI-2 spec. recommends active termination on both ends of the scsi bus. - Improved resistance tolerances (from 1% to about 3%) [Editor(GF): - Reduces current drawn from TERMPWR line. In FPT form: - Provides signal overshoot/undershoot clamping on all signal lines. ] Table of Contents ==== QUESTION: How can I tell whether an unmarked terminator is active or passive? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== If you have an Ohm-meter of one kind or another, measure the resistance from the TERMPWR pin to an adjacent GROUND pin. Reverse the probes and take another reading. If the reading is about 30.5 Ohms, with the probes both ways, you have a passive single-ended terminator. If the reading is about 45 Ohms, with the probes both ways, you have a passive differential terminator. Active terminators should read much higher and give very different readings with the probes interchanged. Table of Contents ==== QUESTION: Where can I buy terminators ? ANSWER From: Rodney Brown (RBrown@cocam.com.au) Info taken from Usenet postings by: John Zatler (JPZ@Popmail.mcs.com) Steve Schreppler (schrep@oasys.dt.navy.mil) Dave Nadler (nadler@ug.eds.com) ==== DataMate / Methode Methode Electronics, Inc. dataMate Division 7444 West Wilson Avenue Chicago, IL 60656 (708) 867-9600 (800) 323-6858 (708) 867-3149 FAX WWW: http://www.methode.com/datamate/dmhome.htm Brief description of terminators available. Passive, Active, SLICK (Elaboration of FPT)) in: Centronics 50 pin (SCSI-1) DM8[05]0-09-[0RS] Male 3 row D-Sub (Old Sun) DM950-??-? Male 50 position .050" Centres (SCSI-2 HD) DM20[05]0-02-[0RS] Male 68 position .050" Centres (SCSI-3 P cable) DM2050-02-68[RS] Male & Female for ribbon cables DM1050-02-[0RS] (M), DM650-06-[0RS] (F) Male/Female for pass through between device and ribbon cable DM550- 06-[0RS] Newark Electronics stocks the DataMate product line. Newark Electronics (International orders) 4801 N. Ravenswood Ave. 500 N. Pulaski St. Chicago IL 60640-4496 Chicago IL 60624-1019 (312)-784-5100, (FAX (312)-638-7652, TLX 6718690 NEWARK U). WWW: http://www.newark.com/ Selectronix Ltd Minerva House, Calleva Park, Aldermaston, Reading, RG7 8NE, UK Tel: +44 (0)118 9817387 Fax: +44 (0)118 9817608 WWW: http://www.selectronix.co.uk/ Cables To Go http://www.cablestogo.com/ Technical Cable Concepts Inc. http://www/techcable.com/ Table of Contents ==== QUESTION: What is Plug and Play SCSI? ANSWER From: leefi@microsoft.com (Lee Fisher) (Updated Dec 7 1993) ==== Plug and Play is the name of a technology that lets PC hardware and attached devices work together automatically. A user can simply attach a new device ("plug it in") and begin working ("begin playing"). This should be possible even while the computer is running, without restarting it. Plug and Play technology is implemented in hardware, in operating systems such as Microsoft Windows, and in supporting software such as drivers and BIOS. With Plug and Play technology, users can easily add new capabilities to their PCs, such as sound or fax, without having to concern themselves with technical details or encountering problems. For users of mobile PCs (who are frequently changing their configurations with docking stations, intermittent network connections, etc.) Plug and Play technology will easily manage their changing hardware configuration. For all users, Plug and Play will reduce the time wasted on technical problems and increase their productivity and satisfaction with PCs. The Plug and Play technology is defined in a series of specifications covering the major component pieces. There are specifications for BIOS, ISA cards, PCI, SCSI, IDE CD-ROM, PCMCIA, drivers, and Microchannel. In a nutshell, each hardware device must be able to be uniquely identified, it must state the services it provides and the resources which it requires, it must identify the driver which supports it, and finally it must allow software to configure it. The first Plug and Play compliant products are available now, as are development kits for drivers and hardware. Twenty different Plug and Play products were shown at Comdex in November 1993. Specifications: The Plug and Play specifications are now available via anonymous ftp at ftp.microsoft.com in the \drg\plug-and-play subdirectory. The files are compressed in .zip format, and are in Microsoft Word format.) Plug and Play ISA files (.\pnpisa\*) errata.zip Clarifications and corrections to pnpisa.doc isolat.zip MS-DOS testing tool to isloate ISA PnP hardware pnpdos.zip Plug and Play device driver interface specification pnpisa.zip Hardware spec for PnP ISA enhancement vhdlzi.zip Hardware spec for PnP ISA enhancement Plug and Play SCSI files (.\scsi_ide\*): pnpscsi.zip Plug and Play SCSI specification proposal scam.zip SCAM (SCSI Comnfigured Auto-Magically) specification Plug and Play BIOS files (.\bios\*): apmv11.zip Advanced Power management spec v.1 vios.zip Plug and Play BIOS spec escd1.zip Spec for optional method of storing config info for PnP BIOS PlayList@Microsoft.COM alias: There is an alias, PlayList@Microsoft.COM, which you can email and get on a Microsoft mailing list related to Plug and Play, where the Hardware Vendor Relations Group (HVRG) will mail out new specifications, announcements, information on workshops, Windows Hardwware Engineering Conference (WinHEC), etc... Compuserve PlugPlay forum: There is a forum on Compuserve, GO PLUGPLAY. This forum is the method for support, discussions and dialogs about Plug and Play. In addition, the forum's library contains all of the current specification. Intel Plug and Play kits: If you are interested in Intel's two Plug and Play kits, either "Plug and Play Kit for MS-DOS and Windows" or "Plug and Play BIOS Enhancements Kit", FAX your name and company information to Intel at 1.503.696.1307, and Intel will send you the information. Table of Contents ==== QUESTION: Where can I get drivers (ASPI and other) for the WD7000 FASST2 host adapter? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== Western Digital stopped producing WD7000 FASST2 cards some time in 1990. Future Domain bought the rights to produce them. Future Domain was later bought out by Adaptec and the boards are no longer produced. Columbia Data Products Inc. of Altamonte Springs, Florida still provides driver support for the card. Their SST IV driver package provides support for many types of SCSI devices including disks, tapes, and CDROM. Also included in this package is an ASPI manager driver (equivalent to the Adaptec ASPI4DOS.SYS). I have personally tested this ASPI manager and it works with GNU tar w/ASPI and the Corel CDROM driver, so most other ASPI stuff should work too. Versions of SSTASPI.SYS prior to Oct 1993 do NOT work with the above mentioned programs so be sure to check the file date. There are other useful programs in the package as well. For instance I find the TAPEUTIL program very handy for duplicating tapes. The price of this package is $99 or $85 as an upgrade of a previous version. A pre-requisite to run this software is that the adapter card must have a BIOS ROM version of 3.36 or newer. I don't think cards manufactured before 1989 or so are compatible. Columbia Data Products Inc. 1070 B Rainer Dr Altamonte Springs, FL 32714 (407) 869-6700 (main number) (407) 862-4725 (fax) http://www.cdp.com (Columbia home web page) cdp@cdp.com (Columbia e-mail) [Update to above information 1/20/97][Editor(GF)] From: "Alan L. Welsh" <snapback@ix.netcom.com> Subject: Western Digital 7000-Fasst SCSI Cards and CDP's SST software Alan L. Welsh, President Columbia Data Products, Inc. We don't usually recommend that users purchase the upgrade for the 7000 software today. Development has ceased, Windows 95 is not supported except in DOS mode, and today I would rather recommend a popular currently manufactured Local-bus SCSI board and not an ISA 7000 board. However, there are still some companies that we do support that have standardized on 7000s and need to keep them in service for years to come. So please buy the software, sell the board, use it as-is, or buy a new board. http://www.cdp.com cdp@cdp.com --------------------- HISTORY OF THE WD-7000 SCSI HOST ADAPTER AND COLUMBIA DATA PRODUCTS, INC. Starting in early 1987, Western Digital (WD) manufactured virtually all of the 100,000+ 7000 SCSI boards, except for a few hundred that were made by Future Domain. The first few thousand, known as 7000-ASC boards went out with no software and only a ROMBIOS that was actually written by John Sponger of WD. In the summer of 1987, Columbia Data Products (CDP) completed and shipped its first ROMBIOS for the card that enabled it to boot and operate in DOS. At that same time, CDP also completed a DOS ram-resident driver, so that DOS would recognize and operate the card without the slowness of the ROMBIOS, a DASD driver so that DOS could access additional drive letters, and to break the (then) 32 meg barrier, and partitioning software to perform the FDISK function for SCSI. It was CDP's goal at that time to develop and provide SCSI software that would enable: any SCSI host adapter, to run any SCSI peripheral, on any operating system, in any PC-based bus. Since at that time WD had 80% of the hard drive controller market, CDP chose WD as the most logical choice to strategically market with, and so CDP supported their cards almost exclusively. During that following year, CDP continued to develop the software for the 7000 host adapters, enabling it to run faster than any other board of its time, including Adaptec's new 1540, whose hardware was actually faster. In the fall of 1988, CDP exclusively licensed its SCSI software suite, called SST to WD. The WD 7000-asc SCSI host adapter was renamed 7000- FASST. WD was the first OEM to ship software with all SCSI boards distributed as part of the package. CDP's SST software was well received, even though SCSI was still a relatively small market. CDP was paid a royalty for each card shipped and CDP provided complete software support and limited hardware support throughout the world. By 1991 CDP had developed support for all SCSI peripherals known, all PC operating systems such as Unix, Xenix, Windows, Dos, Netware, and even AIX, although never officially released, and a SCSI toolkit utility package. All of the 7000-FASST's shipped had multiboot capability that allowed all of these operating systems to simultaneously coexist on a single hard drive so that one OS can be selectively booted each session. CDP's exclusive was ending with WD, and CDP was porting the software to 25 of the most popular SCSI host adapters. Unfortunately, most of software had to be re-architected and rewritten to embrace not only all the new adapters but also the new SCSI software standards such as CAM, LADDR, ASPI, INT-4b, as well as CDP's own standard since 1987, SDLP. During the next few years WD was losing a considerable amount of money and sold many of their product lines, which included selling the SCSI board business to Future Domain. Future Domain did very little sales of the 7000 as they had competing product lines and didn't understand the value of a bus mastering SCSI board. (Bus mastering gives the card the ability to move data to and from the card and system memory directly without the CPU's involvement, making it as fast as the peripherals driving it, even on an old slow 80286!) The bus mastering 1542 product line from Adaptec is still being produced today, very popular, and is based on the same basic design as the 7000. From a pricing standpoint, the prices for this class of product has declined less than 50% in ten years. This is only amazing if you compare the price of 1MB of memory at $300 in 1987 to that of today. CDP has continued to develop and support for the 7000-FASST continuously, even though the board hasn't been manufactured for quite a number of years. Our last major revision of our SST-IV software was done in late 1993, although there have been some minor revisions since then. To enable CDP to continue to develop software and support the board, CDP has been selling upgrades to the large installed user base for years. Without this revenue, development and support would have ceased long ago. There are no plans to continue development at this time, as SCSI is moving from the ISA bus to Local Bus. Although Window-95 development and support was considered, the potential upgrade business wouldn't have covered the cost of development. In 1994 CDP entered the server backup software market, shipping the first version of Snapback in March of that year. Many of our customers for years had been begging us to write our own backup software and were complaining that "restoring" their servers sometimes took days with the current backup products. For SCSI software development purposes only, CDP had been backing up and restoring hard drives containing multiple operating systems for years. CDP adapted and then rewrote this software in this first release to provide the ability to backup and restore any hard drive that contained any operating system, from DOS. CDP later wrote a device driver in Netware, that could make the backup tape look, act and perform like a hard drive from a Netware workstation. This enabled direct file retrieval and use through Netware from the backup tape, making it appear to a workstation to be just another drive letter. Since all the directories and FATs are cached, the tape is almost as fast as a hard drive. Another feature, resize, allows a Netware server's hard drive to be replaced with a larger one in an hour instead of a day's labor. At fall COMDEX 1996, CDP released its latest version, Snapback Live! That backs up a live image of a Netware file server's hard drive, capturing all open files in the process, without impacting system performance. Watch your Computer magazine for Snapback reviews in 1997, as well as a version for NT. Innovating backup software has now become CDP's new life--from an innovative SCSI software company. For more information, contact us at: http://www.cdp.com OR cdp@cdp.com Table of Contents ==== QUESTION: What if I have a SCSI drive larger than a gigabyte (1024MB)? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== The IBM PC/AT BIOS Int 13h disk interface was specified in about 1986 when a large disk drive was about 60 MB. IBM decided that disks wouldn't have more than 1024 cylinders and only allocated 10 bits for the CYL parameter to the INT 13h interface. By 1989, this was already a problem. When vendors began to support SCSI drives under INT 13h, they needed to come up with a translation algorithm between the CYL, HEAD, SECT parameters of INT 13h and the linear block numbers used by SCSI devices. Various vendors chose to map the two such that each INT 13h "cylinder" contained 1 MB. In other words they emulated a drive with 32 heads and 63 sectors per track. At the time, large drives were at about 300 MB, so this worked OK. Once drives larger than 1024 MB arrived, a problem developed. They couldn't provide cylinder values greater than 1023! Changing algorithms became necessary. This is painful since any disk formatted with the old algorithm can't be read using the new algorithm. By the way, different vendors chose different mappings, so drives formatted with one adapter can't necessarily be moved to a different one. Adaptec's newer adapters (e.g. the 154xC and the 154xCF) provide a BIOS control to select the old algorithm or the new one, and they also provide BIOS PROMs for the 154xB that will use the new algorithm. There is an absolute limit of 16 M sectors which means 8 GB assuming 512 byte sectors. Also DOS only allows 2 GB per partition. The day when this presents another problem is not too far away (1995?) Hopefully, we'll all be running more sophisticated O/Ses that bypass this limitation by then. Table of Contents ==== QUESTION: My SCSI bus works, but is not reliable. What should I look at? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== If you still have problems after you're sure that you have all the ID and termination and cable issues resolved, it's time to dig a little deeper. If you get your SCSI bus to the point where it basically works, but it isn't reliable I have found that the gremlin can be the TERMPWR voltage. With your system fully powered up, and both terminators attached, measure the TERMPWR voltage at the far end of your bus. It needs to be between 4.25 and 5.25 Volts. Many vendors start with the system's +5 VDC and add a regular silicon rectifier diode and fuse in series. Silicon rectifiers have an inherent voltage drop of .6 to 1.0 Volts depending on the current through them. Schottky barrier rectifiers are much better for this application. I always use a 1N5817 myself. If the diode on the host adapter is a 1N400x type, change it to a 1N5817. If you add up the drop across the diode and the fuse and 15 feet of ribbon cable and the connector contact resistances, many times you'll find yourself below 4.0 Volts. When using passive terminators, this can shift the signal threshold and decrease the signal to noise ratio on the bus. If you aren't able to get relief with these methods, sometimes you can solve the problem by having several devices supply TERMPWR to the bus. Sometimes the voltage is high enough, but there is too much noise on the TERMPWR line. This can cause really strange problems! If you can see more than about 200 mV of noise on TERMPWR, add a .1 uF and 10 uF capacitor from TERMPWR to one of the adjacent GROUND lines. You need to have the bus as active as you can get it when measuring the noise. I have actually seen over 1 Volt of noise in some severe cases. Another way you can help to solve TERMPWR problems is to use active terminators. These don't draw as much current from the TERMPWR source and they also have a built in regulator which can operate on lower voltage than the standard passive terminators. The regulator also tends to reduce the noise. Table of Contents ==== QUESTION: Where can I find information about programming using the ASPI interface from DOS and Windows? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== The Adaptec BBS has some documents about ASPI. They also have a WWW server. See the FAQ Question "How can I contact Adaptec?" for phone numbers and URL information etc. ftp://ftp.adaptec.com/pub/BBS/adaptec/aspi* Dr Dobb's Journal March 1994 issue pg 154, has an article called "The Advanced SCSI Programming Interface" by Brian Sawert. Example code in C and x86 assembly language is included. The code can be obtained via anonymous ftp from: ftp.mv.com: /pub/ddj/1994.03/aspi.zip. Table of Contents ==== QUESTION: How do I replace Macintosh internal HD and terminate the SCSI chain properly? Answer From: Jie Yuan PhD (Jie.Yuan@UC.Edu) ==== The factory installed Macintosh internal HD should be terminated. Make sure the terminator/resitor-package is installed in the drive before using it. Most vendors will install the terminator for you if you tell them it is for use in Macintosh as the system disk. Manufacturers usually have toll free numbers for SCSI termination, ID, and such. If you don't already have the terminator, they may send you one for free. BTW, Macintosh SCSI chain starts at the system disk (ID=0), and ends at the control board (ID=7). ID numbers from 1-6 should be used for any other devices on the chain. Table of Contents ==== QUESTION: Will attaching a SCSI-1 device to my SCSI-2 bus hurt its performance? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== Attaching a SCSI-1 device to a system with a SCSI-2 host adapter and several SCSI-2 devices already attached will not hurt over-all performance significantly unless it doesn't handle disconnect/reconnect well. This assumes that the host adapter keeps track of protocol options separately for each target device. Some people have the idea that attaching a SCSI-1 device to a SCSI-2 bus will cause the entire bus to run at SCSI-1 speeds. This is not true. Table of Contents ==== QUESTION: Can I connect a SCSI-3 disk to my SCSI-1 host adapter? Can I connect a SCSI-2 CDROM to a SCSI-3 host adapter? Can I connect a Narrow SCSI2 disk to a WIDE SCSI3 host adapter? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== Questions of this nature really cannot be answered in a useful way. There are so many aspects and options to each of the SCSI standards, you need to be much more specific about what devices and adapters you're interested in connecting. Most of the time the best thing to do is just try it! Most combinations will work, but if you're considering a purchase and looking for a guarantee from "The Net", forget it. The issue is further complicated by the fact that vendors like to latch onto the latest acronyms before they even know what's involved. For example SCSI3 is not approved yet, but vendors are already saying their devices are SCSI3 compatible. Since there is no standards compliance testing organization, they can pretty much say what they want. If you buy a high end host adapter (probably called SCSI3 :-) ) from a reputable vendor, and it has enough control over the various options (like synch xfer rate 5,10,20 xfers/s and the ability to disable WIDE or FAST/Ultra negotiation), and you carefully think out what devices you connect to it (all WIDE devices nearest the host adapter end of the bus etc.), and you are careful to properly terminate not only both ends, but both halves (upper byte and lower byte) of the bus, and none of the older devices you might already have (like a Panasonic CDROM) do anything stupid (like not handle the WIDE negotiation message without hanging) then it will all work fine. :-) Even though a host adapter may be called SCSI3 doesn't mean it can enable or disable each optional feature, yet this is vital for supporting older devices. To make matters worse, you won't know which older devices do some of the stupid things unless you know someone who's been bitten already. Your best bet is to look for good deals on name brand devices and adapters and before you buy, ask in comp.periphs.scsi whether anyone has tried the combination you're considering. It's also important to buy from a well known vendor with reasonable return policies. If you're looking at buying a Vendorxyz spiffydisk which claims to be SCSI-3 compatible and you have a Seagate ST-01 host adapter and you want to know if anyone else has tried this combination, then that's exactly what you should ask. In general, most SCSI devices and adapters made less than 4 years apart will probably work together, but without specific information about exactly which devices there's no assurance of it. There's also the potential for poor performance even if it does work. Table of Contents ==== QUESTION: Can I connect a WIDE device to my narrow SCSI host adapter? QUESTION: Can I connect a narrow device to my WIDE SCSI host adapter? ANSWER FROM: Gary Field (gfield@zk3.dec.com) ==== Yes, you just need an appropriate adapter. Most WIDE devices use the 68 pin "P" connector so you need a 68 pin to 50 pin adapter. You do need to make sure that both the upper byte and lower byte of the bus will be properly terminated though. Some adapters provide a place for terminators, others do not. If the wiring adapter is placed right at the SCSI host adapter, you can usually configure the host adapter's on-board terminators to only terminate the high byte. You need to be clear on what type of connectors are present where you want to do the conversion. You also need to plan your bus so that all the WIDE devices will be at one end and all the narrow devices will be at the other end. Certain host adapters with auto-termination make the assumption that when the low byte is terminated the high byte is also. When using WIDE/narrow adapters this assumption is not valid. If for some reason you attach a WIDE device to a narrow bus, you must be sure to disable WIDE negotiation in the host adapter BIOS or the device will hang when it is accessed. One further caveat is that if narrow devices are attached to a WIDE adapter, the adapter's ID must be between 0 and 7 because narrow devices would not be able to see it if the ID was any higher than 7. WIDE to NARROW adapters are available from: Technical Cable Concepts 1790 E. McFadden Ave. Unit 103/104 Santa Ana, CA 92705 TEL: (714) 835-1081 FAX: (714) 835-1595 http://www.techcable.com/ MegaHaus 2201 Pine Drive Dickinson, TX 77539 E-Mail megahaus@phoenix.net Order Line 800-786-1157 Fax Line (281)534-6580 Main Line (281)534-3919 http://www.megahaus.com/ Dalco Electronics P.O. Box 550 275 South Pioneer Blvd. Springboro, OH 45066-1180 http://www.dalco.com/ Warning: I am told that some 68 pin to 50 adapters have TERMPWR wired incorrectly such that some of the 4 TERMPWR lines on the 68 pin connector get connected to the pin opposite TERMPWR on the 50 pin side. This pin was originally a GROUND signal (in SCSI1 spec.) and was later changed to OPEN to prevent shorting TERMPWR if the connector was reversed. Also, some of these TERMPWR lines might be connected to the RESERVED pins adjacent to TERMPWR. Some drives interpreted RESERVED to mean "OK to connect to GROUND" and therefore attaching one of these will also short out TERMPWR. The proper wiring is for all 4 TERMPWR lines on the 68 pin side to connect to the one TERMPWR line on the 50 pin side and leave the RESERVED lines not connected. Table of Contents ==== QUESTION: How does device ID numbering work with WIDE vs NARROW devices? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== Narrow SCSI devices can only use IDs 0 through 7. WIDE SCSI devices on a SCSI-3 system with 68 pin P cables, can use IDs 0 through 15. It is generally wise to reserve 0-7 for narrow devices though. SCSI-2 only specified the use of IDs 0-7 even for WIDE devices, but SCSI-3 allows 0-15 for WIDE devices. All devices on one bus must have unique Ids of course. The arbitration priorities are as follows: highest ID 7 ... ID 0 ID 15 ... ID 8 ID 23 ... ID 16 ID 31 ... ID 24 lowest A WIDE device that is set to ID 10 knows not to respond to selection for ID 2 because the parity bit P1 (for bits 8-15) will not be set by the initiator. During a selection of ID 10, the P parity bit (for bits 0-7) will not be set by the initiator, but the P1 bit will be. To use both WIDE and narrow devices on the same bus, the host adapter must be set to ID 7 (or less) so that the narrow devices can talk to it. Table of Contents ==== QUESTION: What is spindle-sync and why would I want it? ANSWER From: Roger J. Hamlett (Roger@ttelmah.demon.co.uk) ==== It fundamentally affects just one aspect of performance, the 'latency'. With a single drive, if you are waiting for a sector to 'arrive' round a track, you have (on average) to wait for approximately one half the rotational time of the drive for it to arrive. So you might arrive at the track just as the sector has gone by, and have to wait one whole rotation at the worse, or the sector might arrive just as you want it, and latency would be zero. This average time, is the minimum latency achievable. There are two methods of reducing this time. The first is to increase the rotational rate of the drive. This is why for certain types of application a 7200RPM drive, will still outperform a 5400RPM drive that has the same data rate off the drive. The other method is to have multiple copies of the required data on unsynchronized drives, and take whichever copy arrives first. This can be done with mirrored drives, and gives a small improvement in the latency time. However the 'down side' of multiple drives comes when we have to wait for all the data parts to arrive. So (for instance) on a striped array, if the drives are synchronized, the latency will remain the same as for the single drives with both data 'parts' arriving together. However, if the drives are unsynchronized, the 'total' latency goes up, to 33% 'worse' than the single drive, as we now have to wait for both parts to arrive. Similar 'extensions' take place with other RAID configurations, unless the drives are synchronized. Basically, in RAID arrays, the drives should be synchronized, _unless_ the total required data can be assembled from a small fraction of the drives. RAID 1, and RAID 10, are the commonest configurations where synchronization is not advised. Table of Contents ==== QUESTION: What are the general steps I need to do to install a SCSI disk to be used with Windows? ANSWER From: Roberto Waltman (rwaltman@bellatlantic.net) ==== This description assumes an Adaptec host adapter, but other types should involve about the same procedure. Let me start from scratch and describe one by one all necessary steps: Prepare a bootable MS-DOS floppy (SYS A: ) containing, in addition to the system files, the FDISK.EXE and FORMAT.COM programs. (Preferably the ones that came with your Win95 distribution). Make sure there isn't anything in the AUTOEXEC.BAT or CONFIG.SYS files that could make trouble later. Better still, delete these two files. Do not insert the floppy yet. Reset your computer and enter the BIOS setup, (not the SCSI setup) and make sure that the "disk type" is set to 'none' or 'not installed' or something similar. Verify that the boot sequence is A: first. Exit and reset (If your host adapter is new, you can probably skip the next step, but if you want to avoid mysteries later, itís not a bad idea to do it.) Enter the SCSI setup (CTRL-A) and go to the setup menu. Press F6 to restore all the default settings. Exit and reset Enter the SCSI setup (CTRL-A) and go to the utilities menu. Make sure you see your disk in the list of devices, and the name and model look OK. Select the proper disk and run the "Format" Choose Verify media" to build your confidence that the drive is really working right. If these two steps work ok, your disk and controller are fine and they are communicating correctly. If not, you have a hardware problem. (check cables?, terminators?, TERMPWR?, disk itself?) (It is not necessary to wait for the verify function to finish, although it is a good idea to do it with a new disk.) Exit and reset. Boot from the floppy this time. While the system is coming up, a message on the screen will show up saying something like "<your disk model> C: 80H BIOS Installed." This means that the SCSI controller recognized the disk, and since there is not an IDE C: disk, it installed the necessary BIOS functions to use the SCSI disk as 'C:' It does NOT mean that the C: drive is ready for DOS/Windows. If you don't get that message check that the SCSI disk is installed as device ID 0. (With newer host adapters you can use Ids other than 0) After getting the A:> prompt, run FDISK. Create a primary DOS partition. (2 GB max except for Win 95 OSR2 w/FAT32). Make that partition active. Exit and reboot from the floppy. At this point you already have a C: drive, but you can not use it because it has no file system. (Typing DIR C:, for example, will produce the error message 'Invalid media type', different from the 'Invalid drive specification' you got before) To make a file system run FORMAT C: /S /U. The /S tells the format program to copy the system files to C: at the end of the formatting. This will make C a bootable disk. (Assuming the partition was made active above ) When the FORMAT program ends, you should be able to switch to C:, do a DIR, etc. Remove the floppy, reset and (hopefully) reboot from the hard disk. Notes for mixing IDE and SCSI disks on the same system? The IDE disk must be defined properly in the BIOS setup (disk type= number or autodetect instead of "not installed as above"). If you will only boot from the IDE disk, the SCSI disk doesn't need to be made bootable. (Some modern BIOSes let you choose to boot from SCSI even if an IDE disk is installed) The BIOS in the SCSI controller will install a maximum of two disks. If you have an IDE disk installed, the SCSI BIOS will still install the (first) SCSI disk. If you have 2 IDE disks You'll have to install SCSI drivers in the boot disk to access the SCSI disk or disks. If you have a system with 4 SCSI disks (no IDE) the controller's BIOS will install only the first two; Again you'll have to install drivers to access the rest, etc. Table of Contents ==== QUESTION: My SCSI CDROM only works when Windows 95 is installed. How can I get Windows 95 installed? Is this a catch 22? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== Since Windows 95 generally is installed from CDROM media, obviously your system needs to be able to read a CDROM before you can install Windows 95. This is done by creating a boot diskette containing the necessary drivers to allow the SCSI adapter to talk to the CDROM drive. For a system with an Adaptec 2940 host adapter this means: Make an MSDOS bootable floppy. Add the drivers youíll need (as mentioned below) and the MSCDEX program to the floppy. Create two files on the floppy as follows: CONFIG.SYS: LASTDRIVE=I DEVICE=ASPI8DOS.SYS /D DEVICE=ASPICD.SYS /D:MSCD000 AUTOEXEC.BAT: MSCDEX /D:MSCD000 /M:12 /L:J If you have a different host adapter, find out from your manual what the equivalent driver names are for your card. Once you get the system booted, select drive J (the CDROM), and run SETUP.EXE Table of Contents ==== QUESTION: Under Windows 95 OSR2 I can only see the first 8 GB of my 9 GB disk. Whatís going on? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== The retail version of Windows 95 is limited to 2 GB per disk by the use of the FAT16 filesystem. Since youíre getting more than 2 GB, you must be using a FAT32 filesystem. Using FAT32 with drives larger than 8 GB requires a host adapter that supports the "INT 13 extensions". If your host adapter was built before about 1996, you may not have this feature. For example Adaptec 2940W Host adapters did not support this. Even the early 2940UW didnít have it. As of BIOS ver. 1.2x the support is present. Check with your host adapter manufacturer for an updated BIOS. Table of Contents ==== QUESTION: Are there any storage related reasons to upgrade to Windows 95 OSR2? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== Yes, Microsoft has made a few enhancements: FAT-32 filesystem which has the following features: Default cluster size of 4k bytes for drives up to 8 GB. Supports drives up to 2 Terrabytes (2048 GB). Will only install on drives > 512 MB. Can use the "backup" copy of the FAT if needed. Is ONLY accessible from Windows 95 OSR2. (Not supported by Windows NT) CDFS (ISO-9660) enhancements. Drive Power Management. 120 MB floptical support. The mini-port driver for the Adaptec 2940xx (\windows\system\iosubsys\aic78xx.mpd) is updated. In the retail version of Windows 95 there are problems with the Microsoft supplied driver. If the above mentioned file is older than April '96, you need a new one. The updated driver is also available from http://www.adaptec.com/. For more information, see the Win95 OSR2 FAQ. Table of Contents ==== QUESTION: I changed the host adapter in my system and now my disk doesnít work. Why? ANSWER From: Gary Field (gfield@zk3.dec.com) ==== Each manufacturer chooses their own algorithm for converting cylinder, head and sector to a SCSI logical block number. If you run into this, you need to back up your system to tape or CD-R using the old host adapter, switch host adapters, low level format the disk (using the host adapter's BIOS), re-partition (using FDISK), and re- initialize the filesystem (using FORMAT), then restore all the data from the backup media. Not as easy as you expected huh? Table of Contents ==== End. ==== _ -- --/* Gary Field - WA1GRC, Digital Equipment Corp., 110 Spit Brook Rd M/S ZKO3-3/T79, Nashua, NH 03062-2698, phone: (603) 884-2543 email: gfield@zk3.dec.com http://fieldnet.ne.mediaone.net/ TZ=EST5EDT My wife says I don't listen to her; At least I think that's what she said. */