IBM SCSI /A
@8EFE.ADF - IBM PS/2 SCSI Adapter
C8EFE.ADF - Init file for @8EFE.ADF
ZM5 Firmware Uses 27C256 (Thanks
to Rick Ekblaw for these images)
SCSI BIOS 92F2244, 1991, for PS/2 Caching
SCSI controller. 27C256
SCSI BIOS 92F2245, 1991, for PS/2 Caching
SCSI controller 27C256
Terminating the IBM
The old SCSI Adapter /A
Swapping BIOS chips for >1GB Support
Complex BIOS Levels for >1GB IML
Support (Type 1 and 2 ONLY!)
New BIOS Improvements
Multiple SCSI Device Order
The Short SCSI /A (>1GB support!)
OS/2 v.3 SCSI Controller switches
FRU 15F6561 / 85F0002
|F1 PTC Resistor
T-RES Term pack
Y1 25MHz (old) 20MHz (new)
Y2 20MHz (old) 12.5MHz
ZM1 Adaptec AIC-6250EL
ZM5 Microcode 64F5801
ZM26 SCSI BIOS Even 64F4376
ZM27 SCSI BIOS Odd 64F4377
The SCSI Adapter/A lacks auto termination. For proper
termination of the SCSI chain, you will need to either use the internal
T-Res or the external terminator.
ECA 032 Explanation
The old non-cached adapter can be identified by the FRU 15F6561on
the lower left hand corner of the component side of the card. Some adapters
may have been updated.
The old card, Y1 is 25MHz and Y2 is 20 MHz. On the updated
adapters, Y1 is 20MHz and Y2 is 12.5MHz. Yellow wires may or may not exist
on any level of the card. If PN 85F0002 is present, it is the latest level
and does not need to be replaced. If you have either of these versions of
the 15F6561, replace them.
Joe Kovacs says
The original IBM 32-bit SCSI (without cache) worked OK with HDs,
but lost bits with CDROMs. So an engineering change was specified,
and it was patched with a couple of wires in the upper right hand corner,
becoming an 85F0002..
The reworked 15F6561 cards I have seen have the rework wires
just about dead center (FAIR). Not sure if this is it...
The SCSI Adapter is a 16-bit Micro Channel
bus master adapter that features an 8.3MB per second burst data transfer
rate, 16-bit data path with 32-bit address capabilities, and can be installed
in either a 16- or 32-bit system card slot.
The bus master capability of this SCSI adapter
optimizes data flow from each SCSI device configured to the system. This
capability can provide performance benefits in applications where multitasking
or high-speed data flow is essential. It allows the processor to be off-loaded
from many of the input/output activities common to DASD transfers. This SCSI
Adapter also conforms to the Subsystem Control Block (SCB) architecture for
Micro Channel bus master.
Is the SCSI /A SCSI-2?
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 which boot from ID (0)
or (1). It can handle even Ultra-SCSI drives, because SCSI is compatible
in any directions - other than shit-IDE.
These SCSI adapters have a single bus that provides both
internal and external SCSI bus connectors. For these adapters, devices
are logically ordered depending only on adapter slot number and the
SCSI IDs of the devices. NOTE: IBM
SCSI adapters that use a SCSI BIOS earlier than the 92F2244 / 92F2245 pair
will require the IML drive to be SCSI ID6.
The SCSI w/Cache is a "Single Ended" SCSI controller, which
means that every signal has GND as return line. The other relevant SCSI
standard of "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
Now, i got 4-1gb 0662's w/cd-rom in my 9595-omt--
the problem is this--win3.1 does'nt see all of these only 2 -0662's and
cd-rom. Ref disk sees all 5 w/cd-rom. I just added 2 0662's and not sure
what's on them. I tried "fdisk" and "dos" but their not there. Any suggestions?
Scsi "id's" are as follows.
From Brad Parker
Hi Bob, Using the ANSI/IBM standard, I would set the ID's as follows:
id 6 boot drive (c)
id 5 2nd hd (d)
id 4 3rd hd (e)
id 3 4th hd (f)
id 2 CD ROM (g)
Because the standard gives the greatest SCSI bus priority
to the highest numbered drive and the lowest priority for the lowest numbered
drive. If you have more than one partition on each drive, then the drive
letters may change, but the device IDs will stay the same. In fact, I might
just set the CD to id 0 to give yourself room for future expansion :-)
I have five HDs, three floppies, a 6 disc changer and
a Zip drive on one of my 95s, of course I have two host adapters....
New BIOS Improvements
(From Tim Clarke)
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) or
The system partition is no longer restricted to only
Each fixed disk ID will be searched for a valid system
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"
Multiple, redundant partitions are useful if drive id. 6
fails. 'Recovery' can be automatic without 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.)
Autotermination Capable Adapters or Planars
> 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 to autoterminate?
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.
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 O.K.
Enable Termpower or Not?
Back in the "good old times" there was a fairly common problem
with the TERMPWR: if you had an external box and the device was set to supply
TERMPWR as well as the adapter it could happen that the external device tries
to feed back +5V via TERMPWR line into the controller once the "computer"
was turned off. Which often fried the cable and / or blew the TERMPWR fuse(s).
The later standard defined the TERMPWR circuit as a "fuse
/ diode" combo:- the fuse (pico fuse or PTC / auto-reset fuse) to protect
the adapter / device against short-circuits on the TERMPWR line and the diode
to prevent backflow of +5V from external devices to the controller.
So *normally* there should be no problem to have TERMPWR
enabled on all devices - which makes sense on setups with very long cables
and multiple external devices. The importance of TERMPWR is often underestimated
in SCSI-1 environment. Here it is pretty important to feed the TERMPWR line
from *at least* one device to have the proper pull-up on the signal lines
at all. On SCSI-2, where each device *should* have its own active termination
and *should* monitor the TERMPWR and set the termination accordingly it is
of lesser importance. In the worst case one device supplies the termination
at least - if not the host adapter itself.
The main problem occurs, when the TERMPWR line on SCSI-1
setup is interrupted beween two devices and none of the devices supplies
TERMPWR: in this case a proper termination cannot be achieved, because the
(passive) terminator at the end of the chain has no TERMPWR to act on.
Multiple installed IBM SCSI MC/A (w/o Cache)
If more than one IBM MC/A SCSI Adapter (FRU P/N 85F0002 or
15F6561) is installed in a MC-System, and during setup two or more adapters
are shown with same PU/LU setup, or SCSI HD-drives connected to this card(s)
are not correct responding, check the EPROM's in position X5 (ZM5). The
EPROM-P/N in position X5 should be 41G9974.
Ed. Not sure what
this means. None of the SCSI Adapters I have use the mentioned EPROM. Good
Pinouts for the SCSI /A and the SCSI w/Cache
You can see a tableized version of Peter Wendt's observations.
It is HERE.
The long, uncached adapter... This link is to an ECA that concerns a mandatory
Short SCSI /A PN66G1080
The uncached SCSI adapter was available in two different versions as well:
the long card, which cannot handle >1GB and the short card (half card
with microcode dated 1993 and later) which can.
|J1 Internal SCSI Header
J2 C60 External SCSI Port
U2 92F2245 SCSI BIOS Odd
U5 54G1800 512K
U7 92F2244 SCSI BIOS Even
|U8 Intel 80C32GBAA
U9 84F8324 Line Interface
U15 CXK5864BM-10LL 8Kx8
RN1 Bourns 4120R-003
RT1 Bourn 100 HG9K
Y1 20 MHz
Y2 25 MHz
80C32GB- 10MHz microcontroller
as busmaster CPU
J3 Serial Port
Made up name. This is a status link header like on the late
SCSI w/cache. From left to right, the pinout is CHR, ITS, BRN, TXD, RXD,
T-Res for Short SCSI/A
The short SCSI/A use a Bourn 4120R-003 -221/331.
The short card was built by IBM to fulfill longer running
service contracts on old machines after production of the long uncached adapter
ran out. The BIOS ( 92F2244 and 92F2245) is the same as used on the
"later" cached SCSI Adapter so it can support IML drives up to 3.94GB. The
adaptercard itself is an interesting mix of components from the uncached
(long) and later cached (long) SCSI adapters. Works nicely.
chips for >1GB Support
From Peter Wendt
Some time ago Charles Lassiter sent me one of the rare short
IBM SCSI adapters without cache /A ... and I found out, that this adapter
uses the same two SCSI-Bios chips 92F2244 and 92F2245 as the "later" SCSI
adapter with cache. This card however is a strange mix of this "later" adapter
and the uncached ... on half the length.
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 starts
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.
Making Your Own IBM Cable
The actual cable itself is a standard SCSI-1 cable. The unusual
part is the 50 pin edgecard connector. Note that Pin 1 on the adapter is
towards the mounting bracket on the circuitboard side of the adapter. (the
pin on the component side is marked "2").
AdapterID 8EFE IBM PS/2 SCSI
I/O address for adapter. Each adapter must have a unique
3548-354F, 3550-3557, 3558-355F, 3560-3567, 3568-356F, 3570-3577, 3578-357F
DMA Arbitration Level
DMA channel used to transfer data.
< "Level C">,
D, E, 8, 9, B, 1, 3, 5, 6, 7
Bus Arbitration Fairness. Whether the adapter will
release control of the bus when it has been using it exclusively
ROM Wait State Disable
Whether a wait state is added to accesses of the ROM on the
<"Enable Wait State>, No Wait State
SCSI Adapter Address (ID)
SCSI ID of the adapter
6, 5, 4, 3, 2, 1, 0"
ADPItem 1 ROM Address Range
This field shows the address of the 32K block of memory that
is assigned to the adapter. Only one SCSI Adapter will have the ROM
assigned, and any other SCSI Adapter installed will share that address range.
If the ESDI adapter is also installed, then the address of the SCSI adapter
must be greater than the ESDI adapter address.
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