BIOS resetting to defaults. \ VOGONS

BIOS resetting to defaults.

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First post, by flynth

Posted on 2022-12-19, 11:10

flynth Offline

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Joined: 2022-11-11, 10:04

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...

Reply 1 of 2, by Sombrero

Posted on 2022-12-19, 11:35

Sombrero Offline

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Joined: 2021-09-21, 13:43

I had a similar issue and cause of it turned out to be faulty memory. The RAM sticks passed all the tests I threw at them, but BIOS stopped resetting immediately after replacing them.

When I was troubleshooting it I happened to find someone who fixed similar issue by disabling some automatic OC feature you also seem to have or by changing some setting related to that, maybe it's automatically setting RAM speed/timings or something else too high. Also wouldn't be the biggest surprise in the world if the board just has an issue with your unsupported CPU.

If you have RAM that you know to be ok test your system with it alone, otherwise test the system with one stick at a time if you have multiple.

Reply 2 of 2, by flynth

Posted on 2022-12-19, 12:05

flynth Offline

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Rank: Member
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Joined: 2022-11-11, 10:04

Sombrero wrote on 2022-12-19, 11:35:

I had a similar issue and cause of it turned out to be faulty memory. The RAM sticks passed all the tests I threw at them, but BIOS stopped resetting immediately after replacing them.

When I was troubleshooting it I happened to find someone who fixed similar issue by disabling some automatic OC feature you also seem to have or by changing some setting related to that, maybe it's automatically setting RAM speed/timings or something else too high. Also wouldn't be the biggest surprise in the world if the board just has an issue with your unsupported CPU.

If you have RAM that you know to be ok test your system with it alone, otherwise test the system with one stick at a time if you have multiple.

I came back to delete this post as I missed something very basic... But there is already a reply 😀 The CMOS reset jumper was missing. It should normally be in position 1-2 and it is switched to 2-3 to clear, but it wasn't there at all. Once I installed it, it appears the BIOS is retaining its settings.

So thank you for the suggestion, but it turned out to be a simple jumper missing.

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