First post, by flynth
I'm having a weird problem with my Windows XP pc. Specifically the motherboard reverts to BIOS defaults when power is fully disconnected (the CMOS battery was replaced twice).
This motherboard supports "advanced overclocking" and its manual mentions that it helps you with overclocking by reverting bios settings if it fails to boot. However, it doesn't fail, sometimes it simply forgets settings. Interestingly it is much quicker to forget the settings + time than the date, but if the power cable is pulled for less than nger than few seconds it will forget the date too.
The motherboard is Asus M2n68-am se2, the cpu is technically unsupported Phenom x4 940 (black edition), but it works fine except this issue.
I initially suspected the psu, because it is used and it does make a slight noise when power is cut, but I've measured all voltages including standby. I even checked ripple with an oscilloscope and everything is in spec. We'll, standby ripple is a bit higher than the spec for 5v (about 100mv instead of 50mv under 1A of load), but it is unlikely the motherboard will pull 1A off the standby rail. So I doubt it has anything to do with the psu.
Also, I've upgraded bios to the latest with no difference.
Does anyone have any ideas what to check next? I don't usually keep unused PCs powered on and setting up bios every time I start it is getting old...