I have recently installed an Asus P8P67 deluxe into my original system. It works fine except for one issue. If the power has been switched off for about a minute or more (at the wall socket or at the power supply switch) then when switched back on it fails to power on when the PC's power button is pressed. Switching the power off until the green light fades on the board then restoring power then cause it to work but the bios has been reset and requires reconfiguring. Once configured and restarted all works as expected.
Orginally I was overclocking but for testing I simply change a fan setting so I can tell if the bios was reset. The problem is therefore easy to detect and repeat, it is not caused by overclocking or any operating system considerations. My only thought at the moment is the power supply. I am using a Zalman 500W ZM-500HP which worked fine with the previous mobo. It works fine with this new system once running, including overclocked CPU, a decent graphics card, 4GB memory etc. Its been in use for over 2 weeks without unexpected reboots, crashes or similar glitches, except when powered down as described above.
Is it possibly the mobo that is at fault? I have been unable to find others reporting a similar problem.
Any help gratefully received.
Asus P8P67 deluxe motherboard
Intel i5 2500K CPU
4GB Crucial ram
Zalman ZM-500HP power supply
Palit SONIC PLATINUM nVIDIA GTX 460 Geforce 1GB graphics card
It is possible that the CMOS clear everytime you power it off like you describe. But it should not be doing that. I suggest reseting to default and see if it does it still. That mobo restarts to default settings if the oc is unstable, maybe unpluging it from the wall triggers the CPR Mode. If you thing is the PSU starting to fail then disconnect everything else but the essentials for posting. If the problem persist then it might be your PSU not having enough juice.
I had a 600w psu with the same system you have and it failed after a couple of weeks.