A fix that worked for me
Wow. Same problem with my P5K Premium Onyx board. Stored settings in the 2 bios banks remain intact, but the BIOS itself resets along with the time and everything.
Anyone figure this out?
OK, I know people usually frown upon resurrecting really old threads, so apologies in advance, but I stumbled here after working on a P5K that the owner's not ready to replace just yet and starting exhibiting this behaviour when I thought I'd all finished. I'd only just put the side panel back on, went to power up and bang, the CMOS had cleared itself.
So I thought I'd post a fix that's worked in this case for any poor souls encountering the same problem. Afterall, the more good fixes in the pool, the greater the chance it'll be of use to someone.
So the long and short of it is a E6750 at default clocks and 4GB of DDR2 RAM. The machine was upgraded with an SSD some years ago, and whilst quicker than the HD, it never quite reached its full potention due to the AHCI that Asus had to remove from later BIOS' due to licensing issues.
Anywho, I'd been reading about people having success enabling AHCI by using modded BIOS updates or cross-flashing with a P5KR BIOS. So armed with AFUDOS 211 and a bootable USB, I finally plucked up the courage to try this out. Buoyed by the knowledge I had a working P5K BIOS chip to hand in case the flashing went south.
So I got AHCI working (but be warned, the boarded loses use of 2 of the 5 SATA ports and the JMicron controller only wants to work in IDE mode and not AHCI now, but it's worth the responsiveness AHCI adds). But when turning on after power was previously removed, the machine POSTS ok, one beep, goes through the BIOS splash/logo screen, detects the JMicron drives ok, says "Checking NVRAM" and then bang, two beeps in quick succession and dumps out to the black screen with the bit at the bottom that says Date/Time not set, blaa blaa, CMOS not set, whatever, Press F1 to enter setup and F2 to Load default values and continue. Entering BIOS Setup shows a complete reset of all settings - even the date/time.
Tried the usual, another new CMOS batt, strip the board down to bare minimum, different RAM, different CPU. Nothing helped. A lot of people in other forums point to a bad board. But then I thought, it actually POSTs ok after a cold start. It's only after that it resets and clears the CMOS. Knowing that ASUS boards have this feature called CPR (CPU Parameter Recall) which resets the BIOS in case of a boot failure when overclocking, this behaviour definitely looked like CPR in action.
Also knowing that the P5K (and numerous other Asus boards) apply a small overclock default, I figured it was worth turning that feature off. So you have to switch AI Overclocking from Auto to Manual and then I simply left the CPU, FSB, RAM speeds/multipliers etc on Auto.
Save changes and the problem is gone.
Hope this saves someone tearing their hair out.