Y'know, I never thought I couldn't get my Shuttle board working with a P233MMX...
...well, I did.
So I would only get crashes (SUWIN errors during 95/98 setup, SCANREG errors under 98SE, and sometimes the motherboard doing a "halt-then-crash-and-catch-fire" among other things) with the P233, yet nothing with the P133. I initially chalked it up to a faulty component on the board (like the regulators heating up or the chipset not being able to handle the bus speed of the P233...) but no it was way simple than that. Read on please.
Today I decided to give it another go, set the jumpers correctly, until I found a weird jumper on the board. JP44. (on this picture it is closed, but when I initially got the board, it wasn't):
So I thought "what if this jumper was the key to get my P233 working?", and it is!
I remembered at that moment that someone on this forum said (can't remember who) that the first Pentiums (based on the P5 core) were very tolerant to slightly higher-than-normal voltages, and since the P133 is a P5 chip... I thought perhaps the P233 (being a P55C chip if my memory serves me right) didn't like off-spec voltages... I put a jumper cap on the JP44 header and fired the system up, fingers crossed...
It's posting, but will it work with Windows?
Well at first I got met with a message saying that the settings were lost (I kinda expected that the BIOS would freak out with the new CPU), so I reconfigured the BIOS and voilà! It started Windows just fine, without any crashes or anything.
To anyone who has a Shuttle HOT-555A board, a Pentium MMX chip and ran into the same issues, check if JP44 is closed, and if it isn't, put a jumper cap on it.
Proud owner of a Shuttle HOT-555A 430VX motherboard and two wonderful retro laptops, namely a Compaq Armada 1700 [nonfunctional] and a HP Omnibook XE3-GC [fully working :p]