I'm having issues with my ATI 4870 x2. Lately (past month or so) it's been crashing a lot. Eg, I run fallout new vegas. The issues initially range from random parts of the screen flickering, to considerable lag, to random red dots appearing, but they gradually worsen and generally lead to windows crashing. This happens pretty consistently when I try it. I occasionally have issues when attempting to display regular things (like, say, my desktop), but those are much more sporadic. Anyone experience this too? Is it likely a defect with the card, or might it be due to something else (overheating, driver issues)? Thanks.
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What PSU do you have? Uninstall all the drivers and then install them again. Is your CPU OCed? I do not know about the read dots but OCing a CPU can crash a computer.
Overheating is possible - my 4870x2s need cleaning fairly often since they get clogged with dust. I would check for dust first and see if it gets better after cleaning out the heatsink.