SCSI FAQ:
Frequently Asked Questions for comp.periphs.scsi
FAQ history: Created by Johnathan Vail ([email protected]) from articles
submitted to him by comp.periph.scsi readers.
Maintained by Johnathan Vail until November 1993.
Current Editor: Gary Field ([email protected])
Where you see reference to [Editor(GF)] that means me.
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. In addition, a recent version can be obtained
via anonymous ftp from:
ftp.ultranet.com:
pub/gfield/scsi/scsi-faq.part*
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.paranoia.com/~filipg/HTML/LINK/F_SCSI.html
OR
http://www.ultranet.com/~gfield/scsi/scsi-faq.part1.txt and ...part2.txt
---------------------------------------------------------------------------
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.
---------------------------------------------------------------------------
Master Table of contents:
Volume 1
What is SCSI ?
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?
Where should the adapter card be placed?
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 buy IDE ?
Is it possible for two computers to access the same SCSI disks?
Is it possible for two computers to access the same SCSI tapes?
What is the problem with the Adaptec 1542C and external cables?
Where can I get SCSICNTL.EXE and other Adaptec files?
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?
What kinds of Optical Drives are available?
Where can I FTP/download SCSI documents and information?
How can I find out about the emerging SCSI standards?
Where can I get various SCSI documentation?
Where can I get official ANSI SCSI documents?
What SCSI books and tutorials are available?
Where can I get information on various disk drives and controllers?
Where can I get technical information and jumper settings for HP drives ?
How can I contact Adaptec?
How can I contact Archive Corporation? (see Seagate)
How can I contact BusLogic / BusTek / Mylex ?
How can I contact Corel?
How can I contact Fujitsu?
How can I contact Quantum?
How can I contact Seagate?
How can I contact Conner Peripherals (see Seagate)?
How can I contact Maxtor?
How can I contact NCR?
How can I contact Philips?
How can I contact Symbios Logic?
How can I contact UltraStor?
How can I contact Tecmar Technologies (formerly Wangtek, WangDAT,
Sytron, and Rexon)?
How can I contact Western Digital?
How can I contact DPT (Distributed Processing Technology)?
How can I contact Future Domain ? (See Adaptec)
How can I contact Micropolis ?
How can I contact Legacy Storage Systems ?
What is FAST SCSI?
SCSI terminators should measure 136 Ohms?
Can someone explain the difference between 'normal' and differential scsi?
What are the pinouts for differential SCSI?
Who manufactures SCSI extenders and Single-Ended to Differential conv. ?
What are the pinouts for SCSI connectors?
Volume 2
What is the difference between SCSI-1 and SCSI-2?
What is the difference between SCSI-2 and SCSI-3?
Is SYNCHRONOUS faster than ASYNCHRONOUS?
Is the 53C90 Faster than spec?
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?
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?
Where can I get drivers (ASPI and other) for the WD7000 FASST2 host adapter?
What if I have a 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?
How do I replace the Macintosh internal hard disk and terminate the
SCSI bus properly?
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 my SCSI-3 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?
------------------------------------------------------------------------------
====
QUESTION: What is SCSI?
ANSWER From: LSD, L.J.Sak@Kub. Edited by Gary Field([email protected])
====
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.
====
Question: What do all these SCSI buzzwords mean?
Answer From: [email protected] (Hennes Passmann)[Editor(GF)]
====
-Host adapter:
The card that connect 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)]
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 contains extra drives that are
used to apply ECC data correction and provide 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.
====
Question: What is the history of SCSI (What is SASI)?
Answer From: [email protected] (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.
====
Question: Can I access SASI drive with SCSI controller?
Answer From: Gary Field([email protected])
====
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.
====
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 <[email protected]>
edited by Gary Field ([email protected])
====
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 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 Unconnected DEVICE B DEVICE C
Terminated (adapter -Terminated)
+------------+----------+-----------+-----------+---------+
| | | | | |
DEVICE A Unconnected DEVICE B Unconnected Unconnected DEVICE C
Terminated (adapter) Terminated
+------------+----------+-----------+-----------+---------+
| | | | | |
Terminated DEVICE A DEVICE B Unconnected Unconnected DEVICE C
(adapter) Terminated
The following ARE NOT allowed:
+------------+----------+-----------+-----------+---------+
| | | | | |
DEVICE A DEVICE B DEVICE C Unconnected Unconnected Unconnected
Terminated (adapter) Terminated
+------------+----------+-----------+-----------+---------+
| | | | | |
Unconnected DEVICE A DEVICE B DEVICE C Unconnected Unconnected
Terminated (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).
====
Question: Is the spacing of connectors on a SCSI cable important?
ANSWER From: Gary Field ([email protected])
====
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 get to be more
important as your bus performance goes up. i.e. with Fast20 is is very
important, but with SCSI1 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.
====
QUESTION: How long can my SCSI bus be?
ANSWER From: Gary Field ([email protected])
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.) ?
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.e
When Low Voltage Differential(LVD) devices are available, this will allow
lengths between the single-ended numbers and the HV Diff. numbers.
Bus width doesn't change the maximum allowable length.
The bus width is independant of bus length or speed.
Notice that I used the term MHz to specify speed since MB/sec.
changes with the bus width.
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.
====
QUESTION: What are the pros and cons regarding SCSI vs IDE/ATA ?
ANSWER From: Gary Field ([email protected])
====
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 <[email protected]>
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?
====
Should I spend the extra money on SCSI or just get IDE?
ANSWER From: Gary Field ([email protected])
====
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 ([email protected])
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 - 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.
====
QUESTION: Is it possible for two computers to access the same SCSI disks?
ANSWER From: [email protected] (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.
On the issue of tape devices, however, O/S' tend to give exclusive usage
to an application. In this way, tape drives can be shared much more easily.
[Editor(GF): CDROM drives can also be shared pretty easily ]
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(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.]
====
QUESTION: Is it possible for two computers to access the same SCSI tape?
ANSWER From: Gary Field ([email protected])
====
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:
o 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.
o The adapter on both hosts have unique IDs.
o Good and common grounding of both systems and the devices.
o SCSI length limits are not violated.
o Make sure both hosts select the same data transfer mode (synch or asynch).
o 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.
====
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 (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.
====
QUESTION: What is the difference between the Adaptec 1542A and 1542B?
ANSWER From: [email protected] (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.
====
QUESTION: What are the differences between the Adaptec 1542B and the 1542C?
ANSWER from: Terry Kennedy ([email protected])
====
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:
o 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)
o Ability to send "start unit" commands on a per-ID basis
o BIOS works with alternate I/O port settings on the adapter
o Ability to boot from ID's other than 0
o Software-selectable termination
o Software-selectable geometry translation
o 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.
====
QUESTION: What are the differences between the 1542C and the 1542CF?
ANSWER from: Terry Kennedy ([email protected])
====
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.
====
QUESTION: Where can I get SCSICNTL.EXE and other Adaptec files?
ANSWER From: [email protected] (Randy Bush)
and Timothy Hu [email protected]
====
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.]
====
QUESTION: What kinds of Optical Drives are available?
The previousanswer From: [email protected] (John Kim) has been
replaced with an updated version.
ANSWER From: Psycho Bob <[email protected]>[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.
bytes per sides used capacity
format size capacity sector per side standard
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 PD
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.
====
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
====
QUESTION: How can I find out about the emerging SCSI standards?
ANSWER From: Milton Scritsmier ([email protected])
====
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 ([email protected])
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 ([email protected])
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.
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([email protected])
For Fibre Channel Association:
http://www.Amdahl.com/ext/CARP/FCA/FCA.html
====
QUESTION: Where can I get official ANSI SCSI documents?
ANSWER #1 From: [email protected] (Kevin Jones)
and [email protected] (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
====
QUESTION: What SCSI books and tutorials are available?
ANSWER From: Gary Field ([email protected])
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.
A new book has been published by No Starch Press, Daly City, CA,
called "The book of SCSI - A guide for Adventurers" by Peter M. Ridge.
ISBN # 1-886411-02-6 List Price $34.95.
ANSWER #2 From: Runar Jorgensen ([email protected])
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.
====
QUESTION: Where can I get information on various disk drives and controllers?
ANSWER: [email protected] (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.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
====
QUESTION: Where can I get technical information and jumper settings for HP drives ?
ANSWER From: Rodney Brown ([email protected])
Update From: Martin C Mueller ([email protected] )
====
HP SCSI Storage Device Support Pages
http://www.hp.com/isgsupport/index.html
====
QUESTION: How can I contact Adaptec?
ANSWER From: [email protected] (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)]
World Wide Web (WWW) URL:
http://www.adaptec.com
[(from: Andrew Lockhart ([email protected]) ]
You can address Adaptec support by email. The address is
[email protected]. 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".
====
QUESTION: What is the telephone number of Archive Corporation?
====
[Editor(GF)]
Archive was bought by Conner in 1993
====
QUESTION: How can I contact BusLogic /Bustek / Mylex ?
ANSWER From: Gary Field ([email protected])
====
BusLogic Inc.
4151 Burton Drive
Santa Clara, CA 95054
Phone: (800)707-7274
(408)492-9090
(408)970-1414 (Support)
BBS: (408)492-1984
Contact: Jerry Tennant (Sales)
Taylor Ellerbe (Support)
WWW: http://www.mylex.com/
====
QUESTION: How can I contact Corel?
ANSWER From: Gary Field ([email protected])
====
Main Number: (800) 772-6735
Tech. Support: (613) 728-1010
ANSWER From: Gerrit Visser ([email protected])
====
WWW: http://www.corel.ca/
ftp: ftp.corel.ca: /pub SCSI is under Multimedia
====
QUESTION: How can I contact Fujitsu?
ANSWER From: Ken Porter ([email protected])
====
Fujitsu FactsLine FAX Back service (408) 428-0456
A six page catalog of available documents can be ordered.
ANSWER From: Mike Henry ([email protected])
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.
====
QUESTION: How can I contact Quantum?
ANSWER From: [email protected] (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 [email protected])
WWW: http://www.quantum.com
====
QUESTION: How can I contact Seagate?
ANSWER From: [email protected] (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
====
QUESTION: How can I contact Conner Peripherals?
====
Conner Peripherals was bought by Seagate
====
QUESTION: How can I contact Maxtor?
ANSWER From: David G North ([email protected])
====
Main Number: (800) 262-9867 (Has FAXback feature for drive info etc)
ftp site: ftp.maxtor.com (New!)
ANSWER From: Eric Van Buren (vanburen%[email protected])
====
WWW: http://www.maxtor.com/
====
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"
====
QUESTION: How can I contact Philips?
ANSWER From: S. C. Mentzer ([email protected])
====
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/
====
QUESTION: How can I contact Symbios Logic?
Answer From: Symbios Logic
====
The latest Symbios Logic PCI-SCSI drivers and documentation are available on
the Symbios Logic BBS at (719) 573-3562 or the FTP.SYMBIOS.COM anonymous
FTP site. The NCRINFO.NCR.COM site still contains standards and
other information.
For literature on any Symbios Logic product please contact:
Phone: (800) 334-5454
(719) 536-3300
Fax: (719) 536-3301
Internet: [email protected]
Technical Support:
Hotline: (719) 573-3016
Internet: [email protected]
WWW: http://www.symbios.com/
====
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: [email protected]
finger: [email protected]
ftp: ftp.primenet.com:users/u/ustor
====
Answer From: Ben Mehling ([email protected])
====
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:
[email protected] (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 [email protected] / [email protected]
The current maintainers are:
Ben Mehling ([email protected])
Phil Colline ([email protected])
====
QUESTION: How can I contact Tecmar Technologies (formerly Wangtek, WangDAT,
Sytron, and Rexon)?
ANSWER FROM: from: Jay Long - ([email protected]) and
Peter Dyballa ([email protected])
====
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
====
QUESTION: How can I contact Western Digital?
ANSWER From: [email protected]
====
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)
Internet www.wdc.com
FTP ftp.wdc.com
AOL (keyword) WDC or Western Digital
MSN (go word) WDC
====
QUESTION: How can I contact DPT (Distributed Processing Technology)?
ANSWER: From: Gary Field ([email protected])
====
voice: (407) 830-5522
FAX: (407) 260-6690
[Editor(GF)]
WWW: http://www.dpt.com/
====
QUESTION: How can I contact Micropolis?
ANSWER: From: Richard Ravich ([email protected])
====
Tech Support: (818) 709-3325
email: [email protected]
WWW: http://www.micropolis.com/
====
QUESTION: How can I contact Legacy Storage Systems ?
ANSWER: From: Gregory Smith ([email protected])
====
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
====
QUESTION: what is FAST SCSI?
ANSWER From: [email protected] (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.
====
QUESTION: SCSI terminators should measure 136 ohms?
ANSWER From: [email protected] (Steve Ligett)
====
Yes, that is what you should measure. Let's see how that is so. The
terminator contains 18 220-ohm resistors from signals to termpower, and
18 330-ohm resistors from those signals to ground. I've drawn that
below:
termpower--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| | | | | | | | | | | | | | | | | |
220 ohms-> R R R R R R R R R R R R R R R R R R
| | | | | | | | | | | | | | | | | |
signals -> o o o o o o o o o o o o o o o o o o
| | | | | | | | | | | | | | | | | |
330 ohms-> R R R R R R R R R R R R R R R R R R
| | | | | | | | | | | | | | | | | |
ground --+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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:
termpower--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| | | | | | | | | | | | | | | | | |
| R R R R R R R R R R R R R R R R R <- 220 ohms
| | | | | | | | | | | | | | | | | |
| o o o o o o o o o o o o o o o o o
| | | | | | | | | | | | | | | | | |
| R R R R R R R R R R R R R R R R R <- 330 ohms
220 ohms R | | | | | | | | | | | | | | | | |
| +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-- ground
| |
| R <-- 330 ohms
| /
signal -> o-/
<our resistor><--------- other stuff that's in parallel ---------->
We're trying to measure that one resistor from a signal to termpower,
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.
====
QUESTION: Can someone explain to me the difference between 'normal' scsi
and differential scsi?
ANSWER From: [email protected] (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.
====
QUESTION: What are the pinouts for differential SCSI?
ANSWER From: [email protected] (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 the FAQ.
How to tell if you have a single ended or differential drive:
- 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. Note
that most drives today are single ended so you usually only
have to worry about this with old drives scavenged from
other systems.
[ Editor(GF): The preceeding comment about differential drives being old
is not valid. 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. ]
====
QUESTION: Who manufactures SCSI extenders and Single-Ended to Differential
converters ?
ANSWER From: Gary Field ([email protected])
====
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: [email protected]
URL: http://www.ancot.com/
Apcon Inc.
17938 SW Boones Ferry Road
Portland, OR 97224
Phone: (503) 639-6700 Fax: (503) 639-6740
Email: [email protected]
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: [email protected]
Rancho Technology Inc.
10783 Bell Court-Rancho
Cucamonga-CA-91730
Phone: (909)987-3966; Fax: (909)989-2365;
E-Mail: [email protected]; BBS: (909)980-7699
URL: http://www.rancho.com/
====
QUESTION: What are the pinouts for SCSI connectors?
ANSWER From: [email protected] (Bob Snively)
[ Edited and expanded by Gary Field ([email protected]) ]
====
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
maybe ground or maybe 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
====
ANSWER From: Gary Field ([email protected])
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 | |
| SIGNAL| DB-25S |
+-----------------+ 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 | |
| SIGNAL| DB-25S |
+-----------------+ 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
-------------------- END of Part 1 -----------------------
SCSI - A Game With Many Rules and no Rulebook? Version 1.2
Copyright Gary Field, 1994-1997 - All rights reserved.
Special Internet edition - Freely distributable for non-commercial use.
Author: Gary Field ([email protected]) - SCSI hacker since 1985
With a little help from my friends.
Last Updated: March 5, 1997
Trademarks:
MSDOS and Windows are trademarks of Microsoft Corp.
Unix is a trademark of X/Open Ltd.
Netware is a trademark of Novell Corp.
OS/2 is a trademark of IBM Corp.
Enough with the legal mumbo-jumbo already!
A little scuzzy humor:
User#1: I just bought myself a new CDROM drive.
User#2: Is is SCSI?
User#1: Of course not, it's a really nice one!
How do I connect all this stuff to my PC?
So you want to play SCSI eh? Be warned, the road can be rough, but the rewards
are great.
The rules of the SCSI game:
o Each SCSI device needs to have a unique identifier (ID) from 0 to 7.
(0-15 or 0-31 if playing WIDE SCSI) The host adapter is usually
given ID 7. Each device must have a different ID.
o It makes no difference what order devices are connected to the
bus in. Any ID can be in any position on the bus.
o There must be exactly two terminators for the SCSI bus.
If you are playing the FAST SCSI game (meaning that you have a
host adapter that handles the FAST protocol and at least one device
that uses FAST mode), then you need to use active terminators.
See discussions about terminator types in the SCSI FAQ list.
With WIDE SCSI, you have the additional joy or worrying about
both halves of the bus. If you have any narrow devices
attached (and you will), you need to make sure that both the
upper byte and lower byte are both terminated, but only at their
respective ends.
o The total length of all SCSI cabling must be less than 20 feet (6 m)
(75 feet (25 m) in the differential version of the game). Or less
than 3 meters for FAST or less than 1.5 meters for Ultra. (Except
on Tuesdays when it's a Royal Fizbin!)
o The cables must flow continuously from one device to the next.
No stubs more than 3" (.1 m) long are permitted.
(SCSI signals are not real bright and if you give them more than
one way to go they'll get totally confused and wander aimlessly
around the bus bumping into each other).
o For minimum trouble with FAST and Ultra busses, keep devices
(which inievitably contain small stubs) spaced at least .3 meters
apart on the cable. Spacing them at un-even intervals is best to
avoid resonant reflection re-enforcement. Yes, this does limit
you to about 5 devices for Single-Ended UltraSCSI.
o All cables used must have an AC impedance of between 90 and 130 Ohms.
This is a tough one! Short of connecting your cables to a RF
impedance meter, you need to have faith on this one. Get your cables
from a vendor that knows SCSI well. Tip: If you keep the cables
really short (like < 2 feet(.6 m) total), you can get away with
murder.
o For best reliability, all cables should consist of twisted pairs
for each SCSI signal. This is not optional in the FAST version.
(for the uninformed, a twisted pair is two wires that are twisted
together to form a transmission line, and not two people who are
into kinky stuff)
o A player may mix flat and round cable as long as the previous five
rules are not violated. In the FAST and Ultra versions you really
need to keep such transitions to an absolute minimum.
o Devices may be located internal or external to the system's case.
The simplest situation being all internal or all external, but
mixing is allowed IF all above rules are followed to the letter.
o At least one device MUST supply power to the TERMPWR line on
the SCSI bus. (see local rules for important details)
Local rules:
o Supplying TERMPWR is usually considered the responsibility of the
host adapter. This TERMPWR voltage must be between 4.25V and 5.25V
with both terminators attached to the bus. If your bus seems to
work most of the time, but is intermittent, get out the scope or
Voltmeter and check that TERMPWR is within the above range. In
addition, the presence of any noise pulses on TERMPWR will really
screw things up. Some external terminators include a capacitor to
help reduce noise.
o It is assumed that all devices are connected to power supplies
that can fully satisfy all the device's power requirements (even
during the device's peak load). Also, avoid ground loops by plugging
the system and all external devices into the same outlet if possible.
These two rules are often overlooked and can result in severe hair
loss.
o Some vendors may require that any hard disks to be supported
by the PC BIOS (Int 13h) interface, be given ID 0 and ID 1
respectively. Check your manual for this one.
o Because of the nature of the PC BIOS INT 13h interface, users
with drives larger than 1024K bytes (one Gig), should prepare
for extra fun. (see the comp.periphs.scsi FAQ for details)
o Disks formatted using one SCSI adapter cannot necessarily be
moved to another adapter without re-formatting. I'm referring to
the hgher level formatting here (FORMAT.EXE under MSDOS). This
is because the various vendors didn't standardize on a CYL, HD,
SECT to SCSI LBA translation algorithm. (So that's why they told
me to buy a tape drive!)
o Some software will allow devices to be powered on only when
needed. Other software, may require all devices to be powered on
when the system is started. It is recommended that you start out
with all devices on until you get everything working.
o Some devices power up/down cleanly and will not disturb a running
SCSI bus, others do not. If you tell the doctor "It hurts when I
do this", he may well reply "Then don't do that".
o Most vendors properly key the 50 pin connector on the device,
however, it shall be the responsibility of the player to make
sure that pin 1 is really connected to pin 1 everywhere.
o Smoking is a bad idea, even for SCSI devices. Some vendors don't
provide a fuse in the TERMPWR line. Forwarned is forearmed. I'm
personally very partial to those polymer self healing fuses!
If you bought a device or adapter from a company that was too
stupid to include current limiting on the TERMPWR line, by all
means put one of those babies on there. You want one rated for
about 1.1 Amps hold current with < .2 Ohms of resistance.
o SCSI vendors should provide connectors that are called for in the
ANSI SCSI spec's. Some will try to pass off 25 pin connectors on
unsuspecting players. These vendors need a good slap. Feel free
to harrass and ridicule them at every opportunity.
o Connecting and disconnecting devices to/from a system while it is
powered on is seriously discouraged. It is strictly verboten on any
system that caches disk operations (like Unix) since you don't know
when bus activity might occur. A word to the wise should be
sufficient on this one.
o A SCSI device mounted in an external case needs two connectors so
that proper bus chaining can be maintained. In an apparent attempt
at sick humor, A small number of vendors have played a joke on their
customers by supplying only one connector. If you are a victim of
this joke, you need to put this abomination at one end of your bus.
"Flow-through" terminators are available to help solve the
termination problem.
Hopefully, you haven't fallen for this prank more than once!
(Fool me once - shame on you. Fool me twice - shame on me!)
o While the SCSI spec. indicates that a device with ID 7 will get
highest priority during bus arbitration, this rarely needs to be
considered. You might start thinking that you would like your
hard disks to be at the highest IDs. Well, here's where reality
sets in - some SCSI adapter vendors require that the disks be given
ID 0 and ID 1. The bottom line is - Don't sweat the small stuff!
Except in high performance systems with busses fully loaded with
well implemented SCSI devices, you probably wouldn't notice the
difference anyway.
A word about fair play:
o Please don't use unshielded cables for SCSI connections outside
your computer's case. Many of us use the radio spectrum for
something other than a trash heap. Keep your SCSI signals to
yourself, no-one else wants them. If it makes you feel any better,
the shielding will also help keep your microwave oven and hair
dryer from talking to your disks. They rarely say anything worth
listening to.
The object of the game:
o A player must construct a working SCSI bus using the devices and
adapters supplied to him by multiple vendors.
o This SCSI bus should be no longer than necessary to attach all
the given devices.
Wive's tales:
o Some players will tell you that they needed to connect a third
terminator or only use one instead of the required two. These
players do not realize that these symptoms are the result of having
broken one or more of the other rules. Sometimes, plugging in
terminator resistor packs backwards or using cables of too low
impedance can fool these players into thinking these things are
necessary. Forgive them, for they know not what they're doing.
Remember there aren't very many experts in real life, but there
is a real abundance on the Internet!
Judging:
o The computer will be the final judge of adherence to all of the
above rules.
o The SCSI game is unusual in that everyone can win! (Well, at
least those who are smart enough not to buy IDE devices)
The above rules only cover the hardware aspects of SCSI. Without software,
you'll undoubtedly find that your newly constructed SCSI bus is rather boring.
Software is a whole 'nother game!
----------
SCSI software game: (Also called DRIVERS)
Completion of the above hardware game is a pre-requisite.
A little history of the game:
Whereas the SCSI hardware game has strict rules, the SCSI drivers game has been
pretty much a free-for-all. Once, there was total chaos in the land of SCSI.
Each vendor provided driver software for the specific devices it decided to
support. If a player later decided he wanted to attach a device that was
not deemed valuable by their chosen vendor, tough! And to make sure that
a player would not write his own drivers, these vendors would not provide
interface spec's for their host adapters. All vendors supported hard disks,
but attaching tapes, or CDROMs was not for the faint of heart.
One wise vendor called Adaptec, eventually heard the wailing cries
of it's customers and decreed that henceforth SCSI drivers would talk to their
host adapters via a protocol to be known as ASPI (Adaptec SCSI Programming
Interface). Since ASPI was deemed by many to be too simple for serious players,
the ANSI committee came to the rescue with their CAM (Common Access Method).
(Unfortunately, they were a little slow in arriving and most players had
already learned to live with ASPI).
These driver interface definitions changed the SCSI software game forever!
Modern players in SCSI software are frequently heard reverently speaking
these acronyms. The ASPI definition covers MSDOS, Windows, Win32 (95 and NT),
OS/2, and Netware. CAM covers Unix in addition to these.
Still, selection of one of these standards is something of a religious act
of faith. NCR (Now Symbios Logic) wisely chose to support both by
implementing CAM as their native interface and creating an ASPI interface
that goes down through CAM to the adapter. (CAM cannot be implemented on top
of ASPI since CAM is a super-set of ASPI.)
These days, in the MSDOS/Windows world, selection of SCSI software is pretty
much a matter of choosing ASPI or CAM and remaining true to your selection.
In the Unix world, make sure your Unix vendor supports the devices you need
or be prepared to write a driver yourself (lots of fun for the whole family)!
It is rather disappointing that out of all the major Unix vendors, only
DEC chose to implement CAM as their SCSI environment. Even the Linux
developers did their own thing. (Particularly sad since CAM was available
when Linux was being developed).
And so the disks, the tapes and the CDROM all ran happily ever after
and DAT's the end of the story...
If you think you're ready for real fun, be sure to pick up a copy of
the comp.periphs.scsi FAQ from these fine sources:
(latest version posted to Usenet during the first week of each month)
comp.answers:
comp.periphs.scsi:
ftp.ultranet.com: gfield/scsi/scsi-faq.part*
http://www.ultranet.com/~gfield/scsi-faq.part1.txt and part2.txt
Parting shot:
Beware the IDEs of Marge!
Individually we're scuzzy, together we're scum!
Don't forget - The early write eats up the WORM!
No sir, the terminator will not make your SCSI bus stop running.
Yes, I'm afraid that even single-ended SCSI busses need terminators at
both ends.
--------
Don't forget to snigger up your sleeve at your friends who use IDE devices.
You can remain smug in the knowledge that the performance of their
systems will be less than yours while doing backups, balancing the household
budget, replying to the month's email queue and playing Doom simultaneously.
The only reason that IDE stuff is still cheaper is because it was cheaper
initially and those damned unsophisticated DOS running wimps don't
appreciate a good I/O system when they see one grumble, grumble, sniff ...
THE END