First post, by Monteto
I have an IBM PS1 2133 (surface mounted 486SX 25 MHz) I have been upgrading lately, and I want to get more out of the system by upgrading the CPU. Currently I am running a 486DX2 66MHz underclocked at 50 MHz in the upgrade socket (I did the necessary hardware hack to get non-overdrive processors working in that socket, thanks to epictronics for the know-how).
I am aware that all the alternatives listed below would require a voltage regulator adapter, further hardware hacking or a processor with integrated voltage regulation to get the necessary 3.45V or 3.3V instead of the original 5V to the processor.
I know there exists some AMD Am5x86 and Cyrix Cx5x86 models that actually support 25x4 MHz for a 100 MHz system, but I haven't been able to come by any of these.
My question is: can I expect 4x33 processors to work on my system underclocked at 100 MHz? Or will they just simply not work? Some sources mentions the Cyrix processors require 33 FSB, but I suspect this is only for maximum performance. There seems to be a lot more of these processors around than the 25x4 ones.
I do not want to switch the crystal for a 33 MHz FSB on this motherboard as I think it will stray to much from the original and I also don't know if I feel competent enough (seems harder on this board than others I have seen modified).
IBM PS/1 2133 540 10 MB RAM 486SX 25Mhz