First post, by NHVintage
Hi all! New here. Been decades since I last worked on building my own PC's and working on these old processors, so some of my knowledge has disappeared into the mists of time, so apologize if this is a dumb question as I get back into 'vintage computing'. I'm working on an old IBM Aptiva. I'm used to seeing multipliers expressed in x factors - 1.5x, 2.5x, etc. IBM has to do it differently, apparently. For my board (a 2176, version A2 the specs list as:
JP3 Processor Bus Factor
Jumper JP3 --- Core/Bus Frequency Ratio ---
3/2: 1-3 & 2-4
2/1: 3-5 & 2-4
2.5/1: 3-5 & 4-6
3/1: 1-3 & 4-6
The board supports 50hz, 60hz and 66.6hz. In theory it only supports up to 200Mhz pentiums, however, I've found other threads here where it's noted they can support the 233Mhz Pentium MMX - some say just set the jumpers for the same as 200Mhz, for example. Someone on this thread mentions using 1.5x and 66Mhz to get the full 233Mhz.
Re: ibm aptiva 2176-f31 cpu upgrade
I guess that I have more to learn (don't we always), I've always thought the x factor essentially meant that you multiplied the FSB times the x factor to get the processor speed. Told you it was probably a dumb question.... so can someone please explain to me how having the multiplier set at 3/2 or 1.5x (which equals 99.9 - effectively 100mhz) gets 233Mhz cpu speed (or 200Mhz for that matter)? My incorrect knowledge would have guessed 3/1 or 3x (effectively 200Mhz).
I am aware of the 2.8v vs 3.3v MMX vs Classic voltage quandry, so I'm looking into coolers and such, but I note that for my processor this site lists a 'core voltage' of 2.8v but an I/O voltage of 3.3v:
https://www.cpu-world.com/sspec/SL/SL27S.html
What's the difference between core voltage and I/O voltage? I was going to assume that the I/O voltage means essentially 'what the CPU can handle vs what it needs' but you know what they say about assuming...
I appreciate any help you may be able to provide. I've tried looking up this stuff but I'm getting conflicting data and caveats and such, so I thought I should go to the folks that actually do this stuff here. Thanks!