I am having strange problems with my motherboard and was hoping for help diagnosing the system before RMAing.
First off, the PC is running right now. The only real change is that I haven't kept the system unpowered when not in use since it first powered on again. I usually completely turn off the UPS when the system is off.
Config
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Gigabyte GA-P55M-UD3 rev1.0 BIOS 12a beta (sandforce fix)
Antec Nine Hundred (1st)
Intel i5 core 750 (Stock Cooler)
G.Skill Ripjaws DDR3-1600 PC3-12800 2GBx2(x2)
CreativeLabs X-FI Platinum
Western Digital 1TB
OCZ Vertex LE 100GB (sandforce)
XFX AMD Radeon HD 6950 2GB
Seasonic 750W 80+ Silver (S12D-750)
Sony Optiarc Sata DVD/CD AD-7240S-0B
Problem
Computer won't power on. Case Fans wouldn't so much as twitch.
This PC has worked in the past, with the current hardware and other configurations. I have had no need to remove the cpu or its heatsink since the original install two years ago. Temps have remained favorable.
The PC had done this once before last year. Removing the PSU and booting another system worked fine. I stuck it back in and acted as if nothing happened until now.
Tried a different outlet, a different power cord, directly into the wall (usually attached to a UPS). The PSU boots another computer fine. Disconnected all power plugs except 8pin molex and main into motherboard. Switched BIOS battery, removed battery.
I used canned air to clean all internals (psu, pce, gpu, cpu, etc).
Disconnected all harddrives, optical drive, soundcard, graphics card, fans (case and cpu), USB cables, monitor, case connectors (usb, firewire. not case power button, duh), pulled RAM sticks. Also tried a spare gpu (nvidia 6800 gt).
PCMonitor hasn't shown any heat anomalies while idle or under load. PSU never deviated more than 1% on any rail during any prior tests.
Only other symptoms have been anomalous USB issues. Ex:
My Kindle thinks it is plugged into USB 1.0.
USB Flashdrives copy files slowly (copies some then idles, copies some, ...).
Mice will randomly Double Click.
PCWizard showed USB devices as plugged into USB 1.0 but still said I HAD USB 2.0 plugs.
I tried many different Chipset drivers (Gigabyte, Intel) attempting to solve this, but gave up at least a year ago.
Since it did finally come back after sitting on the workbench for a few hours I can assume that maybe the CMOS reset needed longer than 15min to fix whatever corruption may have infected the BIOS. After the first power failure last year I have left the BIOS at default settings. This problem started from a cold boot. The system had been shut off all night (from the UPS).
What could make a system that is just a motherboard with a cpu+fan plugged into a PSU not even twitch? Why did it finally just work after a few hours sitting on a bench?
