Major issue with Radeon 4850

I built a new system a couple months back and noticed when playing graphic intensive games I would get glitches on the screen. Recently I purchased Left4Dead and everything runs fine at first. After playing for about 20 minutes the graphic glitches get more and more common. Eventually My system just completely powers off. This only happens in Left4Dead after long periods of play. Is it possible my video card is defective OR is just overheating? Ive read that the 4850 has heat issues and I installed a third party heat sink.... maybe I didnt install the heat sink properly..... anyway I ordered a second 4850 from a different manufacturer just to test it out and determine if the original card is the issue or if its something else..

Ideas/thoughts would be greatly appreciated

Ok I checked the Idle temp and it stated that its currently at 70 C

Yeah seems like a overheating element also try clocking it to stock assuming it's been oc'ed

70c isn't bad for that card if i remember but oc can cause artifacts in some cases even though it seems stable.

What aftermarket sink are you using? I'm using zalman v1000 on my 4850 and it idles at no more than 45C.

Is the card OC'ed at all?

As for the temp, that is weird because just turning up the stock fan gets idle temps in the 40-50C range. Open the case and see if you can actually see the fan spin faster as you increase the setting.

Also, are you using the newest drivers?

As for it being defective, it could be. My first 4850 had a short in it so the PS would trip off almost instantaneously. If mine had such a big problem, I suppose yours could have a small problem.

Yep, bad coolers. I'm using a Club3D one with their aftermarket cooler on it. It gives me 32 C idle, 40 at load (Triple boxing WoW). As for benchmarks highest I've seen is 50 C.

I didnt overclock. The heatsink I had came with an external fan speed controller. That was cranked to the max. What I didnt realize is that I had to also bring up the fan speed from within the Catalyst control center in order to make the fan go at full blast. Prior to doing that I think the fan was going at maybe 25% of the speed it was supposed to be running at

Yeah that's fine .

"Graphic glitches" could you be more clear please?

Are you using the Catalyst 8.11 Software Suite?

hmm, 100% would probly be a bit too loud... i would say 80% or less for maximum comfort

^^^I am using a Samsung screen..... but Ive never heard of RTA. What is it and how do I turn it off?

I also experienced the same problem with Obvilion(after i upgraded Catalyst driver to that available from ati website)... So i changed back the catalyst driver to manufacturers version. Then problem solved..

I have a Samsung SyncMaster 2253BW.... how do I turn off RTA with this model?

Is it happening very often?
I don't really know anything to fix this problem other than that it's a faulty card..

what about my 4850. setting it to any fan level dont make changes as far as the sound of my gpu fan is concerned.

any clue?

^^^^I did hit apply changes.... AND its not an issue with the card. I replaced the Visiontek Radeon 4850 with a Sapphire Radeon 4850 and had the SAME issues