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PS/2 System 90 resurrection / maintenance

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First post, by PacificState

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I've just acquired a System 90 in good condition, and could use help in keeping it that way:

- Firstly, it came with 8MB of memory (2x4SIMMs). I initially thought the machine was hung as I was greeted with a white flashing cursor, but a thread here (IBM PS/2 Model 90 XP 486, no post, no beeps, just blinking cursor.) was very helpful; if I wait a minute (and watch the monitor go in and out of stand-by twice!), it boots. I'd like to expand it to 64MB, but it seems hard to find suitable (12/24 chip) memory on eBay; I'd appreciate it if anyone knows of a source that sells SIMMS guaranteed to work!

- Is it worth upgrading the on-board XGA memory (with ZIPs), or getting an XGA-2 adapter?

- Is a floppy recap essential?

- Before I pull it apart, are there RIFAs in the PSU that should be replaced?

Thanks!

Reply 1 of 3, by luckybob

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In order!

smaller memory simms are pretty easy to find on ePay. "guaranteed to work" is something you need to just forget about now. Just be ready to buy extras.

more ram only means higher screen resolution. If you are gaming, you are likely running 640x480 at most, and more ram is just going to sit there.

there is a 95% chance the caps will have leaked on the floppy drive. I have 50+ drives on my shelf, and 49 of them need a re-cap.

probably not. I dont think IBM used the rifa caps that crack and go pop. Honestly this is going to be the least of your concerns.

Once men turned their thinking over to machines in the hope that this would set them free. But that only permitted other men with machines to enslave them. - Reverend Mother Gaius Helen Mohiam

Reply 2 of 3, by red-ray

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PacificState wrote on 2026-10-02, 13:28:

I'd like to expand it to 64MB, but it seems hard to find suitable (12/24 chip) memory on eBay; I'd appreciate it if anyone knows of a source that sells SIMMS guaranteed to work!

They do popup on eBay from time to time, but as for "guaranteed to work" then "dream on"! I suspect that https://www.ebay.com/itm/358017281261 may be what you need, but "EDO FPM" seems questionable.

Which OSs do you plan to install?

Is https://theretroweb.com/motherboards/s/ibm-ps … 8590,-9590-late correct got this system?

Reply 3 of 3, by eisapc

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PS/2 modules with parity can be found easily. I used to scan memory bundles and bid for them if I spot parity modules in the lot. Usually 9/8 chips, sometimes 10/20 or 3/6 not nececarrily 12/24
Its mostly cheaper than buying offers allredy announced as parity modules.
You might need to tweak the presense detect bits to make modules work in a PS/2, that were not intentionally designed for one.
http://mcamafia.de/mcapage0/memorypd.htm
https://www.ardent-tool.com/ is another essential site if you start dealing with microchannel PCs.
comp.sys.ibm.ps2.hardware is a still active newsgroup dealing with these systems.

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