PS/2 FAQ, Section 5

S) 5.0 Adding System and Cache Memory

Q) 5.1  How do I add memory to my PS/2 off the motherboard?

[Test from PC Magazine January 28, 1992]

There are several RAM cards out there for the PS/2 and you do not necessarily need a 32 bit card to get the max performance as will be shown. (all cards tested on a Model 70-A21).

KEY:

 %READ = The read speed of memory using 4K blocks in sequence from 0MB to 16MB
         in relation to motherboard memory writes.
%WRITE = The write speed of memory using 4K blocks in sequence from 1MB to 16MB blocks in relation to motherboard memory writes. (not less than 1MB due to that memory being of the resident OS)
TESTED = The as TESTED config, 8MB of 80ns RAM was used for each card.
   MAX = The maximum memory able to be put on the RAM card in MB.  Though MCA   computers don't allow DMA or direct memory access transfers past 16MB, certain OS's for non-DMA type usage i.e. disk caches and EMS.
  SIMM = 9 bit (30 pin) or 36 bit (72 pin) SIMM requirements.
SOCKET = The amount of SIMM sockets on the RAM card.
256-16 = The size of SIMM it can take in K or MB.
INTEGR = The integration of the card to the system.  BIOS (BS) is the right way and allows all memory to be read at or during POST.  T0 is Track 0 method which is not as per IBM spec. This uses a special driver from the hard drive before the OS loads and thus is not usually cached and is reflected below in slower speeds.  BOTH (BH) of course means both can be used (on the CuRAM if BIOS is used 16MB is max and if T0 is used then 32MB is possible).  T0 also has the problem of not being tested by the system.  Unless the card does this any memory errors do not get mapped out.
  POST = Whether or not the memory is shown on the screen at POST.  All BIOS type card 'POST' their memory, but some do not show it.
BKFILL = Whether the RAM card allows backfill of any deficiencies of the 640k base system RAM, more useful in 1MB systems and can allow 0 wait access through the MCA channel and increase performance on such systems by 50%.
 PORTS = Either (P)arallel or (S)erial included or as an (o)ption. PS means one parallel and one serial included, PPSo means there is an option  for 2 parallel and 1 serial port and so on.  NONE means no ports are provided or offered as an option.
MODELS = The supported models, A = Models 50-65SX, B = Models 70-80 and C =         Models 90-95.  Note if BC is specified it means a 32 bit card.  Cards with only a B designation do not work with 50-65SX or for some reason the Model 90-95 even though it was a 32 bit card.
            ____________________________________________________________
            |   | % | T |   |   | S |  |  |  |  |  |  | I |  | B|    |M
            | % | W | E |   |   | O |  |  |  |  |  |  | N |  | K| P  |O 
            | R | R | S |   | S | C | 2|  |  |  |  |  | T | P| F| O  |D
            | E | I | T | M | I | K | 5|  |  |  |  |  | E | O| I| R  |E
            | A | T | E | A | M | E | 6| 1| 2| 4| 8|16| G | S| L| T  |
            | D | E | D | X | M | T | K| M| M| M| M| M| R | T| L| S  |S
-------------------------------------------------------------------------
AboveBoard  |80 |71 | 4 | 32|9  | 8 | Y| Y| N| Y| N| N|BS| N| Y|PSo |AB
MC          |   |   |   |   |   |   |  |  |  |  |  |  |  |  |  |    |
-------------------------------------------------------------------------
AMS Memory  |66 |46 | 8 | 16|36 | 4 | N| Y| Y| Y| N| N|BS| Y| N|PSo |BC
32DI        |   |   |   |   |   |   |  |  |  |  |  |  |  |  |  |    |
-------------------------------------------------------------------------
Capital     |80 |71 | 8 |  8|9  | 8 | Y| Y| N| N| N| N|BS| N| N|NONE|ABC
OS/RAM 32   |   |   |   |   |   |   |  |  |  |  |  |  |  |  |  |    |
-------------------------------------------------------------------------
Capital     |80 |71 | 8 |128|9  | 8 | N| Y| N| Y| N| Y|BS| N| Y|NONE|ABC
OS/RAM 32+  |   |   |   |   |   |   |  |  |  |  |  |  |  |  |  |    |
------------------------------------------------------------------------
CuRAM MC32  |80 |50 | 8 | 32|36 | 4 | N| Y| Y| Y| Y| N|BH| Y| N|NONE|BC
-------------------------------------------------------------------------
Kingston    |80 |71 | 8 | 16|36 | 4 | N| Y| Y| Y| N| N|BS| Y| N|NONE|BC
KTM 3011-4  |   |   |   |   |   |   |  |  |  |  |  |  |  |  |  |    |
-------------------------------------------------------------------------
MicroRAM    |80 |71 | 8 | 32|36 | 4 | N| Y| Y| Y| Y| N|BS| Y| Y|NONE|ABC
SC          |   |   |   |   |   |   |  |  |  |  |  |  |  |  |  |    |
-------------------------------------------------------------------------
MicroRAM    |80 |71 | 8 | 32|9  | 8 | Y| Y| N| Y| N| N|BS| Y| Y|PSSo|BC
386         |   |   |   |   |   |   |  |  |  |  |  |  |  |  |  |    |
-------------------------------------------------------------------------
Parity+Plus |69 |50 | 8 |  8|9  | 8 | Y| Y| N| N| N| N|T0| N| N|NONE|B
P32010      |   |   |   |   |   |   |  |  |  |  |  |  |  |  |  |    |
-------------------------------------------------------------------------
RAMQuest    |80 |45 | 8 |  8|9  | 8 | Y| Y| N| N| N| N|BS| Y| Y|PS  |AB
16/32       |   |   |   |   |   |   |  |  |  |  |  |  |  |  |  |    |
-------------------------------------------------------------------------
SIMMply-RAM |80 |71 | 8 | 32|36 | 4 | N| Y| Y| Y| Y| N|BS| Y| N|NONE|BC
PS/2 32 bit |   |   |   |   |   |   |  |  |  |  |  |  |  |  |  |    |
-------------------------------------------------------------------------

The winner here was the MicroRAM SC (a 16 bit card).  Both cheap and with many memory options.  The 386 version offers a parallel and dual serial option that would be a wise purchase if you needed those but the 9 bit memory it uses needs to be installed in banks of four and thus in general the SC is the preferred solution offering 100% of the performance of its 32 bit brother in a 16 bit config. (note:  I don't know if the 16 bit cards will work as well with processor upgrades, but clearly they worked as well in the 386/25MHz system and were recommended for the 486 90/95.)

Please note that the 16 bit cards scored just as well in most cases and are less money.  Any card the scored percents of 80/71 operated at 0 wait states. The MicroRAM allows 1 wait state with 120ns and matched memory with 100ns, it will operate at 0 wait states with 85ns memory (this was not tested in this test and is purely from the manufacturers mouth).

As of 1998, ChipChat (313)565-4000 (www.chipchat.com) now sells the MicroRam SC cards.  They have been changed a bit though I think as they no longer work on the Model 90 or 95.  They use four 36 bit 72 pin 80ns parity SIMMs in any combination of 1, 2, 4 or 8MB chips, are compatible with models 55, 57, 70, P70, P75, 77 and 80, but not the 90 or 95.  They are 32 bit cards, but can also be used in a 16 bit slot.  They are also compatible with Win 95 and NT.
 

Q) 5.2  How do I add cache memory to my PS/2?

You can't unless it comes already on the board or you purchase a CPU upgrade card with cache built in.

From Louis Ohland <ohlandl@charter.net>:

Type 1 complexes have a socket to add 256K L2 cache.  Prime Electric Corp. has the 17nS module for $19.95 HERE. IBM P/N: 6451095 is the same as 64F0199

Q) 5.2a How do I add up to 2MB of cache to the SCSI w/cache Adapter /A?

You must use a single-sided 30 pin SIMM. You can solder on some wires and cut some of the traces. The SCSI w/cache uses a peculiar kind of RAS and CAS scheme that resists slapping in any old 30 pin SIMM.

http://john.ccac.rwth-aachen.de:8000/misc/ps2cache/

Q) 5.2b I tried adding 1MB SIMMs to the SCSI w/cache, now it shows 0KB!

   If you use incompatible 30 pin SIMMs, the system will disable the cache. You will see "0KB" of cache under "Change Configuration". Don't despair. Replace the original 512K cache. Run the advanced diagnostics (Ctrl-A), choose Test the System and test the SCSI w/cache. The diagnostics will re-enable the cache.

Q) 5.3  Can I use 4MB modules if IBM only calls for 2MB?

Supposedly you can, but not per IBM.  I had both a 80/20MHz and 80/25MHz here recently with both 4MB and 2MB modules, but forgot to test this when I had the chance.  I don't want to say you definitely can until I or someone I trust has done so.  Until then by the memory at your own risk, it may very well work, but give data dropout at times.

Q) 5.4  Who has memory the cheapest?

Really depends on what memory you are looking for.  If it is SIMMs check www.pricewatch.com, if it is for proprietary IBM memory you are better off looking on comp.sys.ibm.ps2.hardware.

Q) 5.5  Is there a way to identify a PS/2 RAM card or SIMM?

[From Aron Eisenpress <AFECU@CUNYVM.CUNY.EDU>]

If the SIMM slots are 3 on the left and 1 on the right then it is a 2-14.  If the slots are 2 and 2 then it is a 2-8mb adapter.  There was a recall about 4 years ago on 2-14mb adapters that had data integrity problems with 4mb SIMMs, but the problem was not ever produced outside the lab that was reported.  If it is 2-14 and has a sticker then it is probably one of the problem adapters.
However, the recall has expired and IBM is no longer providing replacements.

Q) 5.6  What is the ECC memory option on some of the newer PS/2s?

Normal parity memory allows for error-checking of single bit errors, but if a multiple bit error is encountered it usually will crash or return corrupt data.  Either way there is no provision to correct the error.  ECC (Error Correction Code) memory error-checks for both single and multiple bit errors and allows for correction of single bit errors.

Normal parity uses a single bit to protect 8 bits, ECC uses 7 bits to protect 64. 

Q) 5.6a What is this setting for ECC-P for on my 9585 (all models)?

  ECC-P takes advantage of the fact that a 64-bit word needs 8 bits of parity in order to detect single-bit errors (one bit/byte of data). Since it is also possible to use an ECC algorithm on 64 bits of data with 8 check bits, IBM designed a memory controller which implements the ECC algorithm using the standard memory SIMMs.

http://www.tavi.co.uk/ps2pages/ohland/memory_error_correct.html#ECC-P

Q) 5.7  What cache size do I have/can I upgrade to?

See the listing in section 1.2.  As far as upgrading processor complexes, only  Type 1 complexes (J, K, DX2-66 and DX-50) can be upgraded with L2 cache.

.

DX2-66 and DX-50) can be upgraded with a 256K L2 cache daughtercard.

Non-complex systems that accept L2 cache are the Lacuna 9577 (128K and 256K modules), 9585-xKx and -xNx models (128K or 256K module) and the  8580-Axx (64K of SRAM) 

Please tell ME of other cache supporting systems that can have L2 cache added (don't care about the systems with L2 soldered to the planar!)
.