Gigabyte GA-EP45-UD3P Rev 1.6 Display Flickering


Aug 25, 2009
Dear tech Guru's,

My display flickers constantly (about once a second). The computer runs as normal despite this. I do not believe it is the GPU, CPU, PSU, or RAM. Thus I suspect the mobo. Please help. I also understand you like abundances of information, so here it all is.

I built my computer 2 and a half years ago before heading off to college. Here are the important bits:

Gigabyte GA-EP45-UD3P Rev 1.6 Mobo
Intel Core 2 Quad Q9550
2 Crossfired Sapphire Vapor-X HD4890 GPU's
Corsair HX850W PSU

I have the mobo set to the factory settings more or less (I have things like legacy USB and stuff turned on, but nothing dealing with the actual hardware is modified.) In the past, I had it slightly overclocked (I bought a Zalman fan just for the occasion) and the timings/voltages on the RAM boosted, but I didn't notice any performance increase as a result and set everything back to normal.

The Onset and background:
This is not the first time I have had this problem. In October, I had a similar issue. It started with the computer stuttering. I'm not sure how exactly to describe it, but I'll try. It was kind of like lag when the CPU or HDD is overtaxed, only different. It would just not recognize any input while it was stuttering. Then when it resumed, it was as if that input had never been put in, unlike normal 'lag' where it would just spit out everything you did extremely quickly. This problem resolved itself when the computer started flickering at me, crashed, continued flickering, and finally stopped turning on completely and chirped "Power error" at me. I RMA'd the PSU and that resolved the problem. Temporarily anyways since it's back now.

Yesterday my computer crashed suddenly and gave me that same chirping. It did manage to restart on the second go though, but I was terrified. Today it crashed again while I was playing Crysis. It started flickering, then crashed, restarted itself, and is now giving me this lovely problem. (My prayers it would simply go away were not answered...)

The Problem:
The display flickers on and off about once a second from the moment it turns on. The computer seems to run as normal, or at least will boot to windows and the timer that counts down normally at the "windows failed to shutdown properly screen." That leads me to believe it is not a CPU problem. Since I have crossfired GPU's, I tried each GPU separately to determine if one of them was the culprit. They both resulted in the same flickering. I ran a MEMtest in October when I had the previous issue and that did not reveal anything wrong with the RAM. I have very recently RMA'd the PSU, so I don't believe that is the source of my problems either. As such, I am left with the mobo.

My Thoughts:
It seems to me that my mobo is the source of the problem. Problems with the mobo could explain all my symptoms (the previous stuttering, the power errors, and the flickering). I find it unlikely that I would have PSU problems again unless the mobo is either damaging the PSU or is leading to a misdiagnosis of the PSU.

My Plea:
Please tell me what to do. The mobo is still under warranty, but I don't have the little CPU cover (I discarded it after 2 years because I didn't realize it was a 3 year warranty. I have another floating around I can use but I don't know if it's a socket 775 or not).