My HD 4890 keeps crashing at whenever I run certain PC games (Modern Warfare 2 and Tropico 3). The entire PC crashes, it crashes to white, beige, gray, striped screen, etc. and then goes to a black screen normally. I changed the fan speed with CCC to around 70% and it didn't help. But as soon as I turned down the core clock to 650 mhz it worked (going to try it at different speeds) it stopped. So to make sure it was that, I turned it to default and BAM, less than 5 seconds and it crashes. The whole PC locks up and I can't even Alt-F4 out of it. I need to do a hard restart. I've heard other people have a problem with the fan speed/over heating while some just don't work at the default core clock. Even people who returned the card for another one, have had the same problem with this model. Is the card broken or did ATI drop the ball? Is this the case with every card or am I and some people just unlucky to get broken cards?
Crucial Ballistix 4096MB PC6400 DDR2 800MHz
AMD Phenom II X2 545 3Ghz 6MB AM3 CPU
OCZ 600W StealthXStream Power Supply
Biostar A785GE AMD 785G Socket AM2+ Motherboard
Seagate 500GB LP Serial ATA HD 5900/16MB/SATA-3G
Cooler Master Elite 310 ATX Case w /Window
XFX Radeon HD 4890 1GB PCIe w/Dual Link DVI
EDIT: I've tried it up to 840 mhz (remember default is 850 mhz) and it works fine. Anything above it crashes. I can't send it back to tigerdirect. Should I contact XFX?
EDIT EDIT: Crashes now at 840 mhz. Trying 825.