It seems the issue belongs to the first bank, perhaps a broken solder joint?

https://museo.freaknet.org/gallery/ibm/ps2/st … error-code.html

PS/2 286 only supports 256K simms. Is this model 50?

Cheers,

Is a Model 30-286.

Supports up to 4MB on board.

But being IBM as usual used non-standard modules, you can use 3 chip or 9 chip 1MB modules but have to modify them.

Success! Convert regular SIMMs into IBM PS/2 proprietary SIMMs

pentiumspeed wrote on 2023-10-26, 16:13:

Supports up to 4MB on board.

But being IBM as usual used non-standard modules, you can use 3 chip or 9 chip 1MB modules but have to modify them.

Success! Convert regular SIMMs into IBM PS/2 proprietary SIMMs

but mine are ibm branded!

You have to light candles, create an atmosphere, and whisper the FRU to it as you turn it on... so it knows it's the right part.

BitWrangler wrote on 2023-10-26, 18:14:

You have to light candles, create an atmosphere, and whisper the FRU to it as you turn it on... so it knows it's the right part.

You guys know if are the right part! Vogons is full of extremely competent people 😀

Magic numbers for 1MB SIMMs IBM P/N 30F5360 IBM FRU 74X8637 or do this mod... http://john.ccac.rwth-aachen.de:8000/misc/ps2cache/

BitWrangler wrote on 2023-10-26, 19:12:

Magic numbers for 1MB SIMMs IBM P/N 30F5360 IBM FRU 74X8637 or do this mod... http://john.ccac.rwth-aachen.de:8000/misc/ps2cache/

mmmhh.. I read your link well, it doesn't seem like a difficult job to do, the only doubt I have.. if you look at the photo of my simm with 3 chips (which are the 1 MB ones to be modified) they have 2 identical chips and a different one... why? Is this change also valid for them?

3 chips is same way as 9 chips, just the two chips are 4 bits wide each for 8 bit data, and third chip is 1 bit wide for parity.

Cheers,

pentiumspeed wrote on 2023-10-26, 21:59:

3 chips is same way as 9 chips, just the two chips are 4 bits wide each for 8 bit data, and third chip is 1 bit wide for parity.

Cheers,

yes, but in the modification scheme the connection of the rightmost chip is modified, but my rightmost one is precisely the one different from the other two.

The pinout of SIMM are same regardless of chips, what you need to change the routing from the pinout not the chips as shown on the photos.

Cheers,