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I have this ASUS p7p55d-e pro for about 8 months(got it last July) and for this last 3-4 days I cannot boot without clearing my CMOS.

What I have is:

Seasonic M12D 750W  
ASUS P7P55D-E Pro  
Intel Core i5 760 Quad Core Processor Lynnfield LGA1156  
XFX GeForce® 8800 GT Alpha Dog 512 MB DDR3 Standard (PV-T88P-YDF4)  
2x Corsair XMS3 CMX4GX3M2A1600C7 4 GB DDR3 2X2 GB DDR3-1600 CL 7-8-7-20

I tried to remove all the unnecessary stuff: HD/DVD/pci card/USB cable/etc I tried with only 1 dimm filled, instead of my 4, each one individually. It didn't work.

I tried changing the battery, here goes a few dollars to nowhere, didn't work.

If I don't reset the CMOS it sometime stock on RAM led, sometime on BOOT DEVICE led, when this happen, it stuck on CPU speed detection.

When I boot right after the reset, I MUST click on the F2 option (boot with default BIOS setting) if I go into the BIOS and save/restart, I have to reset it again When booted, everything is rock solid stable, tried memtest, CPU stress, etc, etc. Without issues.

What should be my next step? Trying a new PSU? (I need to find one.) Do RMA? (I need this mb since it's my only computer...)

Something else?

Edit: I just tried with a new PSU, it didn't fix the issue.

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i will add that i did update the bios without issue – Fredou Mar 1 '11 at 1:34
Something isn't right if your board requires this much attention just to boot. I'd consider replacing the board. See this question for further information:… – MaQleod Mar 1 '11 at 3:00
I have the exact same problem. Asus P7P55D-E Pro. Each time I boot, it will either hang at RAM LED, or after powering off and back on, it will hang at Boot Device LED. If I clear CMOS and "press F2 to load defaults and continue" System will boot to my drive and be stable. On very next reboot, system hangs at mem LED again, and I have to repeat the jumper clear. Very strange and very repeatable. Since the problem developed, the behavior has not deviated from this pattern at all. Suggestions? I was thinking PSU also... – user72033 Mar 15 '11 at 9:42
@Akiho try this: clear cmos, F1, ESC, discard, boot, reboot, F1, ESC, discard, boot, reboot, F1, ESC, discard, boot, reboot, this way, i don't have to clear the CMOS at every reboot, so far. the moment that i do a "write" in the cmos, i need to clear it – Fredou Mar 15 '11 at 9:55
It could also be settings for the RAM, such as memory timings etc – Vxed Mar 15 '11 at 14:11

I have the same problem. I have an Asus P7P55D-PRO, it has been having boot problems for the last 6 months. The green standby LED is delayed after switching on the PSU. Then when I press the power button the computer starts only for 1/4 seconds. I've fixed it by clearing the CMOS settings on every boot, the computer starts automatically when the standby LED is on.

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If the CPU is overclocked (running faster than it's rated for), this could be one cause. A failed CPU fan could also be a problem because your processor could be running too hot.

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it's not overclocked and temp is showunder 32c – Fredou Mar 1 '11 at 14:14

The one DIMM you tried might be the bad one.

Bad RAM can give boot problems, and if the parts that are bad are used in the boot process, they can escape testing.

Try swapping your RAM positions and running memtest86+.

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The OP said that he tried each stick of RAM individually. – Kevin M Mar 15 '11 at 13:43
And I suggest putting them all in, not individually and trying memtest86+. The reason is, we had a bad stick causing boot errors that memtest86+ didn't catch the errors when it was stick 0, but did catch the problem when it was stick 1, 2 or 3. – kmarsh Mar 15 '11 at 15:25
And that’s why you try each stick in each slot. Yes, it’s more work, but it’s still faster and easier than doing them all together, getting an error, and then trying to narrow down which stick and/or slot was the problem. – Synetech Feb 8 '12 at 3:39
I see what you're saying... I was referring to a server with a minimum memory slot population requirement. I guess the answer differs a bit depending on the h/w, but the point is the same, test everything in different slots. – kmarsh Feb 14 '12 at 22:05

Are you cutting power to the computer when it's turned off?

I've had this problem with some Asus settings when computer is unplugged. BIOS thinks that it was because of bad overclock and settings need to be reset.

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I did have one system where you needed to cycle power to get a clean boot. It would fail later in the IPL, though, after Windoze began to load. – Daniel R Hicks Dec 7 '11 at 13:23
If the CMOS is reset when the power is cut, it’s usually because the battery is dead and cannot retain the settings. – Synetech Feb 8 '12 at 3:38

Have you considered that you might have a BIOS rootkit? Clearing the CMOS & restoring default settings overwrites the rootkit, but only temporarily, since the trojan somewhere in your system (CD/DVD player memory chip?) reloads the corrupt BIOS after that, which prevents next boot.

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I'm intrigued by this possibility, cause i have absolutely never heard of viruses sitting in cd players, or BIOS. The worst i have heard of is boot sector viruses. Got some links about this? – Journeyman Geek Jul 26 '12 at 9:14

And along with all these good ideas be sure your mobo battery is in good condition. A failing battery can cause odd conditions that are hard to diagnose.

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