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I like to think that I'm pretty hardware savvy, but the fact is that I figure out most of my problems with computers as they come along. I thought I'd ask the big giant heads here a couple of questions before I sink more cash into upgrading my system.

I have an ASUS P2B motherboard, and it works fine. I'm running it at 100MHz FSB (more on that later), and have a P3-500 as the CPU. Since this MB came out in 1998, though, things have changed a bit; the original documentation I have states that this MB is good only up to P2-400 (at 100MHz FSB), and the most current documentation available states that a P3-550 is the fastest it can take. To make things even more complicated, the current manual also states that FSB speeds of up to 133MHz are selectable, as are up to 8x CPU speed multipliers. This would imply (to me) that P3-800 (at 100MHz FSB) should be reachable, or, for that matter, P3-800 (at 133MHz FSB).

Anyone have any insights into these apparent contradictions? Any advice other than "go and buy a modern computer, grandpa"?

(The link refers to a page that allows the .pdf file for the latest MB manual to be downloaded.)

The answer is 'it depends'.
It would depend upon which revision of the mobo and which BIOS you have.

The newer the revision and BIOS, the better your chances of running a P3-800 are, but I will tell you that if you run the FSB at any setting above 100Mhz, you are overclocking that 440BX chipset as it isn't rated for anything above 100Mhz by Intel and it lacks the PCI/AGP bus locks to keep those speeds within spec.

If you want absolute reliability, do not set that FSB on anything other than 66 or 100Mhz. Anything else will cause the PCI/AGP/USB/etc., buses to run out of spec.

Your best bet is to look on Asus's site and see what they say the max is for your revision/BIOS combo. IIRC, a lot of pre P3 BX boards couldn't run the P3 chips because of VRM incompatibilities. If Asus says your board won't run a P3, don't even try or you might fry the board and/or chip.

Glocksman wrote:The answer is 'it depends'.
It would depend upon which revision of the mobo and which BIOS you have.

The newer the revision and BIOS, the better your chances of running a P3-800 are, but I will tell you that if you run the FSB at any setting above 100Mhz, you are overclocking that 440BX chipset as it isn't rated for anything above 100Mhz by Intel and it lacks the PCI/AGP bus locks to keep those speeds within spec.

If you want absolute reliability, do not set that FSB on anything other than 66 or 100Mhz. Anything else will cause the PCI/AGP/USB/etc., buses to run out of spec.

Your best bet is to look on Asus's site and see what they say the max is for your revision/BIOS combo. IIRC, a lot of pre P3 BX boards couldn't run the P3 chips because of VRM incompatibilities. If Asus says your board won't run a P3, don't even try or you might fry the board and/or chip.

I checked the MB/CPU compatability page, and it lists a PCB and BIOS number. If I assume that the PCB is the revision number, and the BIOS version is self-explanatory, then I am indeed stuck with nothing better than a P3-600.

Here's another one: can a faster CPU be "dumbed down" to one which can be handled by the MB? In other words, if I get a P3-700, can I just set the multiplier to 6.0x and make it a P3-600?

(By the way: thanks for your help.)

Probably not due to Intel's changing the VRM spec for the higher speed chips. The CPU will physically fit the slot, but it's electrically incompatible.

IIRC, you can buy a 'slocket' adapter that'll let the S370 CPU's run in the Slot 1 boards but I don't know if they resolve the electrical incompatibility issues.

The best thing to do at this stage is give that CPU/RAM/Mobo package an honorable retirement (or sell on eBay ) and spend $200 or less on a Athlon XP nforce2 mobo/CPU/RAM combo.

I guess there's something I'm not getting here. Looking over the voltage requirements of past CPUs, the P2-233 which originally came with my system years ago used 2.8V. The P3-500 which has been working just fine for some time wants 2.0V. A P3-700 is stated to use 1.65V. The motherboard manual has nothing to say with respect to voltage requirements.

My question is, then, does the MB step these things down automatically, does the CPU draw only what it needs, or is my current system going tick...tick...tick...?

If asus says your mobo won't run the faster CPU's, it's because the VRM can't go low enough.

When I ran a P3 system, I used an MSI slot 1 board with a slocket and a S370 P3 850.
I was lucky enough to get the latest revision when I originally bought the board and it had 'Coppermine' support (VRM and BIOS changes) included.
If I'd wound up with a board that was a revision earlier, I would have been SOL and had to buy a new board, as you can update a BIOS but good luck updating the VRM soldered onto the board.

From what you've said is on Asus's site, forget going to a Coppermine P3 CPU, as it won't support those low voltage cores but if they say your current CPU is supported, you're OK.