CPU doesn’t warm up at all.

Most likely split-rail voltage regulator on your board is just dead. Plain and simple. And if I remember correctly, ASUS boards ignore any split-rail voltage jumpers setting with classic Pentium installed.

The Serpent Rider wrote:

CPU doesn’t warm up at all.

Most likely split-rail voltage regulator on your board is just dead. Plain and simple. And if I remember correctly, ASUS boards ignore any split-rail voltage jumpers setting with classic CPU installed.

Ah that doesn’t sound like good news! Do you know if that would be a fairly small SMD IC chip perchance or one of the black voltage regulators?

I did notice one cap around that area which is sat at an unusual angle where all the other ones are flat - after testing I didn’t think this would be an issue as the board appeared to work but I wonder if replacing that would do any good? It appears to have been done through force rather than the underside of the cap leaking but it could have damaged the cap somehow

Black voltage regulator. If you have doubts about capacitors - recap them too.

britain4 wrote:

I did notice one cap around that area which is sat at an unusual angle where all the other ones are flat - after testing I didn’t think this would be an issue as the board appeared to work but I wonder if replacing that would do any good? It appears to have been done through force rather than the underside of the cap leaking but it could have damaged the cap somehow

If it pulled on a leg hard enough it could have damaged the capacitor, even if the sutures on the top of the can look perfectly fine and you see no other evidence of leakage.

And I just found why I was so confused by it - for some reason i thought a P100 was socket 7 - don’t really know why I thought that but it makes sense now that the board would boot with a socket 5 but not a socket 7.

It sounds like an easy enough replacement if it’s one of the black regs - I’ll get measuring some voltages and hopefully will be able to sort it out 😀

Changing the cap didn’t do any good - same results I’m afraid. The caps are good quality Japanese ones but I thought that one showed signs of physical damage, perhaps not.

So I have the exact same problem. I bought an ASUS P5A a few years ago with a k6-2/333 and it was running flawlessly. About 2 years ago, the board stopped booting, and I thought it was dead. Later I got a P100 and tested the board just for sure, and voila, it's working! Only with this cpu. I already tested with a k6-2/450 and seame problem, doesn't boot. Next month I'll try a P200mmx, to test yet another cpu, but I'm afraid the board will not boot, as this mmx cpu use 2,8v, instead of 3,3v of the p100. At the same time I'll try a P133, and I think it will boot as it is a P54C cpu (same as P100, just another multiplier). The k6's uses 2,2-2,4v. I have to assume that the voltage controller is malfunctioning.
So what can I do? This P5A is a very fine ss7 board, very dificult to find nowadays in good shape.

If I can get mine working OK I’ll give you a shout. Depends whether or not you can solder 😀

Definitely sounds like the same issue though!

I've taking a bit more time with the problem. Unfortunately, it still remains. I can boot a P100 and P133 (P54c cores) but not P166mmx and P200mmx (P55c cores) and any K6. I have yet to try a cyrix pr200, but it is also dual voltage, so I think it will not boot too.
Now, how I can I track the split-rail voltage regulator?