IBM SCSI w/Cache
the IBM SCSI-1 Adapters
OLD SCSI w/cache (Single oscillator)
NEWER SCSI w/cache (Dual oscillator)
NEWEST SCSI w/cache. (Triple oscillator)
10 pin Artifact on Newest SCSI w/cache
Benefits of the new BIOS for the SCSI w/Cache
Swap BIOS for +1GB Support
BIOS Upgrade Needed for >1GB Support
Difference between -C188 and -C186 microcontroller
Specifications for SCSI w/cache (possibly OLD)
Results from upgrading to 2MB cache
OLD SCSI w/Cache (Single
and dual osc)
NEW SCSI w/cache (Triple
Non-Compatible SIMM Results
Converting Standard 30-Pin
8MB Cache Hack?
Testing SIMMs for 2MB upgrade
OS/2 v.3 SCSI Controller switches
Capability- Yellow vs. Orange Termpacks
IBM PS/2 SCSI Adapter w/Cache
Init file for _8EFF.ADF
- IBM PS/2 SCSI Adapter w/Cache
(modified, no ADP, ROM area selectable / German comments)
Making Your Own IBM Cable
The actual cable itself is a standard SCSI-1 cable. The unusual
part is the 50 pin edgecard connector ( Dalco part 40720).
Note that Pin 1 on the adapter is towards the mounting bracket . Remove
the 50 pin dual row header (pry it open or cut it off) and crimp on the
50 pin edgecard connector. Watch pin 1!
NOTE: On original
IBM ribbon cables, the cable exits the edgecard connector TO THE LEFT as
the connector is seated on the internal port. As installed, this means
the cable goes straight up towards the top of the 95 case and away from
other adapters. This makes it possible to route it away from them towards
the front of the case, then down the site of the DASD structure, then to
° IBM Personal System/2 Micro Channel SCSI
Adapter with Cache
The redesigned PS/2 Micro Channel
SCSI Adapter Cache provides system configuration flexibility to support
multiple internal and/or external SCSI devices such as high performance
fixed disk drives, CD-ROM drives, tape drives, scanners, and printers.
It has a burst transfer rate of 16.6MBps, adheres to the industry standard
ANSI SCSI interface and is supported in either a 16- or 32-bit Micro Channel
The IBM PS/2 Micro Channel SCSI Adapter with Cache
is a 32-bit busmaster SCSI adapter containing a 512KB cache buffer that
allows system memory to be totally dedicated to running the application
rather than a portion being reserved for software caching. This SCSI adapter
is recommended where improved data transfer rates and multiple SCSI devices
are required and system memory is constrained. However, 512KB cache
is too small for the LAN Server application.
|F2 Bourns Transorb
U32 80C188 10Mhz-clocked busmaster
cpu (20MHz divided by 2 for more stable waveform)
U44 Hitatchi HM62256LFP-12T
U47 Adapter BIOS 64F5984
U48 OKI 15F7917
|U68 SCSI BIOS, Even
U69 SCSI BIOS, Odd
U73 Adaptec AIC-6250EL Line Interface
U87-U88 30 pin SIMM
Y1 20.0 MHz Oscillator
Pin 2 of the internal port is on the component side. Pin 1 is on the
The "single OSC"-adapter is the "old" IBM SCSI Adapter with cache
/A, which has no internal termination resistor and needs the large external
Terminator block.P/N is 6451018 (FCC-ID:ANO6451018).. This adapter needs
the update SCSI BIOS P/N 92F2244 / 92F2245 in order to handle drives >1GB.
Note: The Adaptec AIC-6250EL Line
interface chip is just "glue logic". It is NOT
While the C188 has (2) 8-bit parallel-ports it only has
an 8-bit external data-path.
ECA 032 Possible Replacement Required
The old adapter w/cache can be identified by PN 64F1333
on module U47 (just below the MMKs). If you have this adapter, replace
Ed. I saw something about potential
data loss concerning this ECA. Not sure- my U47 is the adapter BIOS.
U47 Adapter BIOS, 33F5546
U73 AIC-6250EL Line Interface
|U68 Even SCSI BIOS
U69 Odd SCSI BIOS
U87-U88 30 pin SIMMs
Y1 20.0 MHz Oscillator
Y2 25 MHz Oscillator
FCC ID: ANO6451018 Mostly seen across the pond in Europe. This adapter
needs the update SCSI BIOS P/N 92F2244 / 92F2245 in order to handle drives
>1GB. The "dual OSC"-adapter is the "later" IBM SCSI Adapter with cache
/A, which needs an external terminator.
Ed. Odd, I have a single osc 6451018,
BUT it has the solder pads and the outline for Y2.
Functions of Late Adapter Oscillators
J300 C60 Port
T-Res SCSI terminator
U33 84F8324 Line Interface
U47 BIOS 61G2976
U68 SCSI BIOS Even
|U69 SCSI BIOS Odd
U87, U88 30 Pin SIMMs
Y1 20.000 MHz
Y2 25.0000 MHz
Y3 32.0000 MHz
20MHz oscillator is for the SCSI-Line
25MHz drives the cache controller.
32MHz is for the 80C186-16 microcontroller,
which supplies the busmaster functions. This card is significantly faster
than the "old" adapter
The "latest" cached SCSI, FRU 85F0063 (FCC-ID is ANOSPRIME),
has no Adaptec chip present and a larger yellow 20-pin DIL terminator chip
close to the external port. This card has the strange
10-contact card edge connector close to the internal 50-pin card-edge.
It has a third oscillator as well: a 32.0000MHz (Y3).
Based on Peter's experience, If you have one of the older
IBM SCSI-Adapter or SCSI w/cache *cards* you can use the SCSI-Bios from
the later-level SCSI Adapter with cache (92F2244 and 92F2245) to make the
system capable of handling drives over 1GB IF the complex BIOS is of the
New BIOS Improvements
> Oh, really? Please expound on the "extra features" of the new SCSI
bios. In addition to handling drives >1GB as the IML drive, what else?
The upgrade provides the following additional capabilities:
1. More efficient use of Adapter ROM memory - minimizes adapter
2. BIOS support for fixed disks up to 3.94 gigabytes per device.
3. Supports "Search IML" from any PUN (Physical Unit Number)
SCSI ID. The system partition is no
longer restricted to only SCSI
ID=6. Each fixed disk ID will be searched
for a valid system partition.
4. Allows redundant system partitions (IML).
5. Sharing of SCSI devices. An external SCSI device, such
as the 3511,
may be shared between two system units. The
menu item is "Target"
> So what good is the multiple, redundant partitions? Especially
with a T1-3 complex?
If drive id. 6 fails 'recovery' can be automatic
without the need to recover IML-capability by partially ripping the machine
down to change SCSI Id.s. You do, however, need to have planned for
this and set up the appropriate 'IML/Reference Partition'(s) and 'Active
Partition'(s) on the 'fallback' drives (Id. 5, 4, 3... etc.)
From Charles Lasitter
With the triple oscillator (newest) versions of the Enhanced
SCSI w/cache, I see some Microcode differences but don't see much in the
way of any particular pattern for when one Microcode will be in use versus
One adapter has 10G4890 dated 1991. Another has 61G2976
dated 1993. What is the difference between these two microcodes?
I invariably see the "1993" microcode with some unusual looking cache SIMMs,
but changing them doesn't seem to make a difference. I see "1993" on some
boards labeled as "CARD 1" and others" CARD 3". There is nothing
I can track there.
I can't figure out why they would change it if they didn't
make something better, but I don't know what that would be or how it would
manifest itself. I know that the microcode from triple oscillator adapters
can't be switched to the old unterminated adapters, but I'm uncertain about
from one two another for the same "3-oscillator" family.
From Tony Ingenoso
(guessing) There may have been a change to deal
with the low-power mode problems of certain microcode level Kazuza series
drives... Had to tweak the heads off the cylinder they were idled
over to keep from losing data when the next write (after power restoration)
happened to be on that
cylinder... nasty problem...OS/2 had an ABIOS patch to deal with
it on the pseudo-ESDI versions of the drive.
Roll Your Own
U47 Firmware - 27C512
U68 SCSI Bios - 27C256 (Even)
U69 SCSI Bios - 27C256 (Odd)
SCSI Device Ordering
Older SCSI adapters supported only a single bus which
provided both internal and external SCSI bus connectors for the single
bus. For these adapters, devices are logically ordered depending
only on adapter slot number and the SCSI IDs of the devices.
Maximum SCSI Devices Supported
Narrow SCSI devices support 8 possible SCSI ID values; therefore,
up to 7 narrow SCSI devices can be connected to the internal or external
SCSI busses in any combination using the remaining ID values. Wide
and narrow devices may be mixed on the same internal/external bus by using
the proper combinations of SCSI bus cables, terminators, and/or SCSI connector
Is the SCSI w/cache SCSI-2?
The SCSI adapter on the 8595 is "SCSI-2 compliant" - means: it uses
parts of the *command set* from SCSI-2 (command queueing, command tagging)
but the *transfer speed* is SCSI-1 with 5MB/s. It is also a "Narrow"-SCSI
controller - opposed to "Wide"-SCSI, which means it uses 8-bit devices
and not 16-bit devices.
However: it can handle even Ultra-SCSI drives, because
SCSI is compatible in any directions - other than shit-IDE.
And the controller is "Single Ended", which means that
every signal has GND as return line. "Differential" means, that every signal
has a return line with inversed polarity ... when -for example- +DATA0
sends a logical "1" on the active line the return line -DATA0 sends a logical
"0". The transceiver circuit in the device checks the *difference* between
the two signals (therefore "differential") - line disturbances afflict
both lines at once and are eliminated therefore.
Conclusion: the IBM SCSI adapter is 8-bit narrow, single-ended
SCSI with SCSI-2 style command set and SCSI-1 speed of 5MB/s. It can handle
7 Fast- or Ultra-SCSI devices and can handle even 7 Wide-devices if there
are converters used from Wide-to-narrow SCSI (68-to-50 pin) but these devices
must use device numbers from 0 - 6. The SCSI-ID 7 is used for the controller
itself. First device on IBM SCSI controllers is the one with the highest
ID (6) opposed to Adaptec or Buslogic controllers.
Capable Adapters or Planars
If the card or planar has a red colored T-Res, it does not have
the circuitry to support autotermination (you have to pull the termpack
if you add an external device). If the termpack is yellow, then the
additional circuitry exists and you can add or remove external devices
without having to pull the T-Res off the adapter.
> Peter, for the $64,000 Question. If you use a yellow termpack on a
adapter or board that had a red one initially, will that enable it
Definitely: No. The "Auto-Terminate" is a function that require a little
more hardware: a switching transistor that disables the TermPwr wire from
the T-RES and another transistor / IC function that senses the voltage
on the TermPwr line and the voltage on the data lines to figure out whether
the line is terminated or not.
Fact sheet is HERE
Bourns 4120R-003, -221/331
Model (41 = Molded DIP), 20 Pins, R = Thick Film Low Profile, 003 =
Resistance Code in the format R1 / R2, First 2 digits are significant,
Third digit represents the number of zeros to follow. 220 ohm, 330 ohm.
It looks like this..
From Tim Clarke
AFAIK, there is only one FRU for the "internal" termination
resistor pack for the IBM SCSI w/cache (adapter FRU 85F0063) that
has the appropriate 20-pin socket and the IBM SCSI w/o cache (adapter
FRU 85F0002). The termination resistor pack (20-pin) is FRU 57F2870
and, provided you insert it with Pin 1 correctly oriented, should work
What about that Artifact?
From Ian Brown
Interesting bit of history this. And no, you won't find
it documented anywhere. IBM was one of the members of the organisation
that originally set the standards for SCSI, and as usual they had their
One of these 'unique' ideas was the ability to be able
to set the SCSI ID# remotely from the host adapter rather than having to
set it on the device itself.
The result of this was the 'legacy' small connector on
some 'high end' SCSI hosts, and that awkward RS6000 socket as the external
port, which became the IBM standard for a while.
The idea was good, but be grateful it never took off,
as I understand it required decoding hardware on the devices, which could
have left us looking for special 'IBM SCSI' HDD's etc.
It was never fully implemented as far as I know, SCAM
How did I find out? I went to a 'Big Blue' re-union recently,
and met one of the original designers of the IBM SCSI host adapters. I'd
been wondering about that extra connector for years, so I took the opportunity
to ask him.
on the SCSI w/cache
||SCSI-1 w/SCSI-2 commands)
|SCSI bus path / speed
||8 bit / 5 MB/sec
|I/O bus path / speed
||16 bit / 3 MB/sec
||None (use software)
|Tagged Command Queuing
|Old SCSI w/cache cpu
||80C188 at 10MHz
|New SCSI w/cache cpu
||80C188 at 16MHz
||Type 3 (long)
||One internal; one external
||7 devices per adapter
|Cache std / max
||512 KB / 2MB
||Two 30 pin SIMMs
||0, 512K, 2MB
|Cache write policy
Pinouts for the SCSI /A and the SCSI w/Cache
The edgecard for the SCSI Adapter /A has less contacts than
the later SCSI w/Cache. Still wondering why... But you can see a tableized
version (Thank you, thank you..) of Peter Wendt's observations. It is HERE.
Swapping BIOS chips
for >1GB Support
From Peter Wendt
Today - while juggeling around with parts & cards
on a Model 90 - I decided by what reason to remove the SCSI-Bios from an
old uncached SCSI and stuff that from the "later" cached on it. Earlier
this year I'd tried to swap the entire Eprom-Sets among the old and the
later cached - and it did not work. Today I left the busmaster microcode
Eprom on the card and only swapped the SCSI-Bios.
To my undescribeable surprise: it worked. To make sure that it is not
a gimmick of that machines' Bios I tried it on a Mod. 70-A21, which has
definitely no enhanced SCSI-Bios support in the planar microcode. I pulled
the 2GB IBM 0664 harddisk from my WinNT Server and installed it in the
Mod. 70. I have a heavily modified Mod. 70 - has a standard power-plug
(as described on my page, folks !) and a Kingston 486DX-33 upgrade. I also
installed the uncached SCSI with the old Eproms. No surprise: "No operating
system" and the system halted.
Then I used the 92F2244 and 92F2245 on that same adapter ... Voilà:
"OS Loader V4.00 ..." and WinNT 4.0 Server started up ... ! (Ever seen
that on a Mod. 70 ?) Tried the same procedure with the old IBM SCSI adapter
with cache (the one *with* the AIC-6250EL Line Interface) - with the same
results. Old Bios-chips: No operating system - New chips: Win NT
Conclusion: If you have one of the older SCSI-Adapter *cards* you can
use the SCSI-Bios from the later-level SCSI Adapter with cache to make
the system capable to handle drives over 1GB.
I do *not* know if there is another limit after 4GB - but assume it
is (I don't have drives over 2.2GB currently). This limitation will at
least exist on the IML-machines, since the principle that starts up the
IML cannot handle drives over 3.94GB (the mysterious IML-border) due to
the technical method of putting the systempartition MBR at *the end* of
the physical diskspace. The register width is obviously limited to any
number of total data-blocks below 4GB. So that does not change at all.
Upgrade Needed for >1GB IML Drive
From Tim Clarke
After an extended E-mail exchange with Al Brandt, who
couldn't get a machine to IML from a >1GB drive (SCSI ID. 6) attached to
a SCSI-1 controller w/cache but with the notorious (now infamous?) 92F2244
and 92F2245 'Enhanced SCSI BIOS' ROMs using a Type-1 complex with either
of the 'older' complex BIOS ROMs (i.e. 84F9154 for SOD Type-1 and 91F9812
for non-SOD Type-1), I decided to run my own tests.
'Enhanced IML' in the complex upgrades is the *only* way
to be able to IML from a drive >1GB (and from a drive Id. ¬= 6).
At this time I must assume that the 92F2244+5 ROMs provide
support for drives <= 4GB, but the 'old' complex ROMs' IML support somehow
does not make (proper) use of it, possibly due to bad bit-shifting and/or
masking when 'translating' the 'cylinder, head, sector' information to
and from the SCSI 'logical block/sector' value.
From another thread
BTW, space is usually allocated as a whole no. of
cylinders, so the 'old' 3MB "System/Reference Partition" will grow to ~12MB
on a >1GB drive.Albeit that only the 1st 3MB of that space is used/needed.
Some Other Thoughts
From Charles Lasitter
I've had some VERY entertaining results in my installations,
depending on what other drives were present, and which version of the processor
BIOS was used.
With the 52G9509 in place, ID6 in bottom bay (Mod 95)
at end of cable, ID5 in bay above on next spot on cable, I couldn't get
the IML to go to ID6 to save my ass. It made a beeline for ID5 every
time. Put in the old BIOS, and it goes straight for ID6.
I think there are a LOT of quirks like this (and yours)
to be mapped out, and that seemingly innocuous settings changes in the
ABIOS make differences you'd never guess sometimes.
I also suspect that the Mod 90 is it's very own distinct
bird with it's own eccentricities in this and related matters.
2MB SCSI w/cache
Can I increase the cache to 2MB?
One module that can be used to expand the IBM SCSI Adapter with cache
/A from 512K cache to 2MB cache is the IBM P/N 30F5360 / FRU 74X8637, which
is a 1MB x 9 bit (Parity) 100ns module *with* IBM-specific presence detection.
The above-mentioned IBM modules are in the Mod. 30-286 (8530-Hxx or
-Bxx) with 80286-cpu - if anywhere at all.
MY 1MB SIMMs are marked MSC2314-12YS9A 183004 68X5721.
It has 9 OKI M511000A-1AJ chips, mnf. 89335521
From Jerry Dumer
I have 3 boards with Toshiba THM91010AS-10 simms that do the job fine.
I found these on a memory card in a Model 60. They are gold pins. I imagine
Toshiba made them for the 30-286s. They do work.
Kingston modules labeled KTM-1000/M30 (From Peter)
If you try some likely looking 30 pin SIMMs and they don't
have the correct CAS/RAS wiring, the system will disable them it and you
will see SCSI Adapter w/Cache with 0KB. Don't freak out. Replace the original
SIMMs and run Advanced Diags and test the SCSI Adapter to restore your
512K cache. Been there, done that.
Industry Standard Memory Be Converted?
Yes. Alfred Arnold has finally figured it out. Dr. Jim
Shorney confirms this triumph. The biggest hurdle was the IBM modules have
a different RAS/CAS scheme in addition to the different pin-out. As time
goes on, exceptions MAY be found. News as it happens
30-pin SIMM Hack (To his site)
For those that have the burden of college education, I
made some assumptions. First, the SIMM pins will always be performing
the same function (like parity Data Out, parity CAS). Second, those simm
pins can be used to positively identify the parity chip's DO and CAS pins.
This makes manufacturer's data sheets uneccessary. Assuming
they even have them.
break the connection between SIMM pin 26 and the parity chip's DataOut
pin; This inferrs that SIMM pin 26 goes to Data Out-
connect the parity chip's DataOut pin to SIMM pin 29;
Tie the parity chip's lead that USED to go to SIMM pin 26 to SIMM pin
break the connection between SIMM pin 28 and the parity chip's CAS pin;
Parity chip CAS is attatched to SIMM pin 28
connect the parity chip's CAS pin to SIMM pin 2;
Attatch lead that used to go to SIMM pin 28 to SIMM pin pin 2
connect both SIMM pins 26 and 24 to SIMM pin 22 (GND).
SIMM 26 and 24 tied off to SIMM 22
A picture of Dr. Jim's 2MB
Also: No. It is a little miracle that the 1MB modules
work for the 2MB total cache, but the 4 Meggers are -again- different to
the 1MB ... apart from the presence detection and the RAS/CAS scheme. There
are 1MB modules that behave the same way than the 256K modules - but no
The 4MB you find are either Industrial Parity (9 bit,
but w.o. presence detect) or non-Parity Industrial modules (8-bit). IBM
itself never introduced 4MB modules of that scheme for their own machines.
The PS/VP Series 1 used 1 and 4MB 30-pin modules, but these were "industrial
The PS/2 256K, 512K and 1MB modules are very unique. They
depend -technically- on a very old (1985) Hitachi patent to which IBM only
added the presence detection. From the principle the "Single RAS" scheme
of these modules is similar to the Hitachi HB61009BR-15, 150ns module -
a very antique construct, which were superseeded by the much more common
HB41256-style design, which uses separate RAS/CAS timing for interlaced
access to the cell-array, which then allowes much faster RAM access (typically
100 - 60ns).
Testing SIMMs for
use in SCSI Adapter w/cache
The secret is out... What to look for if $10 for two SIMMs is
too much for you...
From an article by Peter Wendt....
The IBM Adapters with and without cache /A are in fact SCSI-1 adapters
with 5MB/s interface speed (!) to the device. This however does not tell
how high the effective data-throughput might be.
This depends on more factors than just the interface-speed:
- speed of the drive mechanism (track-to-track / average seek)
- adapter-cache (size, speed and degree of optimizing)
- device-cache (size / usage)
- cable and degree of disturbances through line noise / spikes etc.
- termination (reflection of data packets)
- adapter- and device command set (autonomy of device / command queing)
- the adapters chipset
Okay - for the curiousity: I have tested the 2MB-cache in my 8595-AK9
(32MB RAM / Kingston TurboChip / modified BIOS) with 2 different IBM adapters
and a Quantum Fireball TM2110S (2.1GB Ultra-SCSI). This drive is known
as quite fast and should not be the bottle-neck. I used the IBM SCSI adapter
with cache /A in the version *without* the internal termination resistor
and the Adaptec AIC Line interface chip (IBM old) and I used the IBM SCSI
Adapter with cache /A *with* the internal yellow termination resistor and
the IBM SCSI Interface (IBM new).
Here are some test-samples (results are temporary examples)
Results for old
|Weighted Average (KB/s)
new SCSI w/cache
|Weighted Average (KB/s)
Results obtained by reading and writing blocks from 512 bytes to 63.5KB
in linear and random methods.
Read Linear with large data-blocks shows
a 20% gain, due to the 2MB cache.
Write Linear values are only 2 - 5% smaller
in either case.
Write Random values show the influence
of the drive mechanism.
What does this mean in practise ?
1.) Only way to get minimum values up is to use a harddisk with a faster
2.) Combination drive - adapter doesn't reach the data-throughput for
the SCSI-1 interface speed.
3.) Any GUI operating system that uses a temporary swap file operating
with large blocksizes will make use of the enlarged SCSI-Adapter cache
during the swapping process.
4.) Effects are noticeable in Win95 applications and -probably- much
more noticeable on OS/2 and NT, which use the harddisk-subsystem more intensely
than DOS/Windows or Win95. (That's a prediction from my experiences with
5.) If you cannot -by what reason- use a F/W-adapter / F/W-drive combination
(or don't want to) the enlarged cache to 2MB is one simple method to get
out around 10 - 20% better performance of an unmodified system running
under i.e. Win95 (I'd kept this careful - you cannot await wonders if you
have a slow harddrive)
The testing will continue as soon as possible. Like very often
my job came in the way and I needed the 95 (which is usually my network-server)
for the daily purposes again. But this first testing suite shows that the
enlarged cache *has* in fact a good impact on the over-all performance
of the system. I'll try to fix up the results and try bringing them here
- if you like "data cemetries"... the tables are *very* complex and have
hundreds of numbers, which must be set in proper relation to each others.
And must be interpreted the correct way.