Note that my desktop is a dual processor with an empty socket (I've had a Pentium Pro sitting in a drawer for 30 years, waiting) and unfortunately I also need to get a VRM because it was optional at the time. It currently has a 180MHz 256kHz processor and I have a 200MHz 256kHz, so I think it's compatible, the only difference being the 60Hz or 66Hz bus. Is this reasoning correct?

A man after my cold, dead, cholesterol-clogged, heart. <3

To answer your question: The 'official' answer is no, its not 'correct'.

the real world answer is; yea, it should work. The PPRO is pretty forgiving. You can set the multiplier and bus speed to just about anything and so long as the chip is running at or under ~233mhz, it's highly probable it will work. This will depend on the 180mhz chip running at 200mhz, but I would be genuinely surprised if it didn't.

luckybob wrote on 2025-08-28, 14:32:

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A man after my cold, dead, cholesterol-clogged, heart. <3

To answer your question: The 'official' answer is no, its not 'correct'.

the real world answer is; yea, it should work. The PPRO is pretty forgiving. You can set the multiplier and bus speed to just about anything and so long as the chip is running at or under ~233mhz, it's highly probable it will work. This will depend on the 180mhz chip running at 200mhz, but I would be genuinely surprised if it didn't.

To be honest, i want to run the 200mhz one at the original system speed of 180mhz, not the opposite.

AlessandroB wrote on 2025-08-28, 18:53:

To be honest, i want to run the 200mhz one at the original system speed of 180mhz, not the opposite.

I have to be honest, I wasn't expecting to hear that. In that case, there is almost no way it wont work.

I assume the 256kHz -> 256kB cache.

The internal cache is what sets the max useful memory size, add too much and the machine slows down noticeably when accessing uncached ram.

Not on the pentium pro. The PPRO can cache any ram it can address. with 36 bit address bus, thanks to PAE, that's like 64GB.

The cacheable ram limits were a function of socket 7 and earlier chips and chipsets. the 430 series chipsets were the culprits here as anything over 64mb would slow the system. But if the board had an upgradeable TAG ram, this was bypassed almost entirely.

Hmm, I have a different experience with the PPRO - used a number of dual CPU (ABit mobos I think), 200MHz PPRO:s with 512MB ram and just a single CPU with 512kB cache, adding 1GB RAM made a snail of the systems. (still have a spare somewhere)

edit; could be something related to only using a single CPU on the dual CPU setup, the tag ram was integrated with the cache I think.

I mean, there's always an edge case. Without having that exact system in front of me, I can't really make a determination, but I'm just going off the white paper.

I have 1GB in my dual 256kB @233 system with the PR440FX and there is no performance penalty