P5B Deluxe - FSB/PCI-E problem

To keep things simple, I found that I had a problem with my PCI-E lanes dropping from x16 to x1 when I overclocked, and after a lenghty process of elimination, I found that this happened when I increased the FSB.

To be precise, when I increase the FSB to anything above 380MHz, the PCI-E lanes drop to x1.

380MHz:


381MHz:


(Note: I realise that the multiplier is different in each case; this BIOS seems to reset it if I change the FSB and I didn't notice. This is definitely not the cause. Also, I realise that the card is overclocked. This is done on startup by Rivatuner; I have tried with and without overclocking with the same result.)

This is true for every speed I have tested right up to the limit (quite low due to my crummy RAM). I have tried this with a fresh install of XP with WHQL drivers, with exactly the same result, so it has to be hardware/BIOS related. I haven't been able to test another card on this board yet, but if I can then I will.

I have tried this with a few BIOSes, an old one, 1223 and 1226. As far as I can tell it's the same. As I said, I did a lot of testing in the BIOS to isolate the problem, and I'm pretty sure that it's the FSB. I have played around with the PCI-E frequency from 101MHz to 115MHz but it doesn't help.

I am hoping that somebody can help me out here, as I can't push the FSB over 380MHz to do anything remotely 3D.

Thanks in advance!

I managed to fix it. If anyone else is having this problem, I had to set northbridge voltage to 1.45v and southbridge to 1.5v. PCI-E at 101MHz.

Now running at a comfortable 3.4GHz (425x8) with PCI-E x16. Yay.

I had the same problem, and did the same thing to fix it after finding a "Fix" here at OC Forums (but left PCIe at 100MHz).