rmay635703 wrote on 2022-10-22, 02:04:

IBM went to great lengths to cripple their boards from being upgradable. My guess is any chip you install needs to support the o […]
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werfu wrote on 2022-10-21, 19:18:

Had any luck? I got my hands on a PNY Powerstacker (an interposed AM5x86-P75) and I'm trying to get it to work with a PS/1 2133-F43 (originally with a 20Mhz CPU) but I can't get it to POST 🙁

IBM went to great lengths to cripple their boards from being upgradable.
My guess is any chip you install needs to support the overdrive pinout to disable your soldered chip.
Best bet are Intel DX2-4 and p24t overdrives, a 5x86 overdrive would need to support the overdrive pinout and not all did.

Unfortunate that it’s so hard to find BIOs upgrades for all the IBMs, IBM was even stingy in distributing bios updates unless you bought official upgrades from them that required an upgrade.

My school library had original generation IBM model 25 286’s upgraded to SLC chips and they got updated bios’s in the package so the systems actually posted with the correct info.

Have to imagine it was a pretty penny getting IBM certified upgrades let alone having an IBM maintenance agreement and network

Actually my board doesn't have a soldered CPU, it has a socket for both CPU and a 487. I tried both way, with the Powerstacker into the main CPU socket, and in the 487 socket, neither works. The PNY Powerstacker does have the extra pin for being fitted into 487 socket. I'm leaning toward BIOS incompatibility, although I have no real way to know if the Powerstacker itself isn't broken. I don't have another 486 handy to test it out sadly. I'll try to find an ebay listing for 486 DX2/66 5V cpu not too costy and see if works. That at least would be a nice upgrade from the SX25, although I'm not sure the board support 33Mhz FSB.

Just found a picture of a Powerstacker 133 box with a list of non-compatible system. Sadly my IBM PS/1 2133 is part of these.

Looks like I now have a costy paper weight. I might try to find a clone 486 on eBay that won't cost me an arm and leg.

Otherwise, I bought a 486 DX2/66 5V cpu. The system boots, but I'm having weird video issue and the system is unstable. I've been having trouble with my PSU lately. Seems like I'll have to go TFX + adapter for this one.