CPU upgrades, pt. II

From: jpero_at_cgocable.net <(jpero_at_cgocable.net)>
Date: Tue Apr 18 01:49:14 2000

On 17 Apr 2000, at 23:31, Peter Pachla wrote:

> Hi,
> > Heres a PS2/50z question.
> >
> > Mine only has 1meg, looks like 72pin simm but none I have seem
> >work. All of them happen to be 8x32 (16chip).

Must be 36bits and correct presence detection pins set.

There were two or three speeds but same capacity on 512K x 36

> I don't really know too much about PS/2s yet, I'm only just starting to
> investigate these machines (I've got 3 - a Model 50, a Model 80 and a Model
> 95).

x595-xxx? Yes there is 8595 and 9595's.

I upkeep my small set of PS/2s and have researched much, one
newgroups for the ps/2 is out there (comp.sys.ibm.ps2)

> Interesting, my Model 50 has a pair of SIMM sockets on the planar. They look
> more like 30-pin SIMMs than 72-pin ones, but I haven't taken them out to
> check yet. Also, I've never seen SIMMs like these before - the PCB is a
> brown/beige colour, and the RAM chips are in small silver "cans" rather than
> the usual black epoxy.

Allison's is 50z. Yours is the early 50. Users complained of lazy
performance, IBM responded with 50z, better memory subsystem
performance w/ 10mhz 286 cpu (0WS) and faster and tad bigger hd
BTW, those pair of simms are nonstandard 30pin IBM 512K x 9bit
on also nonstandard pinout. 50z uses standard parity 72pin with
correct detect pins set.

> Anyway, I suspect you'll find that the limit for RAM (on the
> motherboard/planar/whateveryouwanttocallit) will be 2Mb. IBM used to make
> these wierd, double sided, 2Mb 72-pin SIMMs specifically for some models in
> the PS/2 family.

Just plucked a 32bit MCA Kignston memory 4 x 72pin slots card
from C.R. for prissy 5 USD. Going into 70-Axx with more of those
hacked 2MB sticks.

> I remember these SIMMs distinctly since around 10 years ago they used to
> sell for practically nothing on FidoNet as they were of no use whatsoever in
> anything but a PS/2.

Those 2MB 72pin parity simms?

Those are common 512K x 36bit 85ns, Most of them can do 80ns
after moving the one SMD resistor one spot. Duly done that to
several and using them in my 70-Axx.

55sx, 50z, 70's and some PS/2 machines that uses these.

Received on Tue Apr 18 2000 - 01:49:14 BST

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