Im having a problem running 2 ATI Radeon HD 4870 1GB with 3D games. The 2 games ive tried are Warhammer online and Spore. While running in Crossfire mode, the whole screen constantly flickers from the point of starting the games, looks kinda like a strobe light. Looking at other posts, ive tried the following:
1) Disabling crossfire. This solves the whole screen flicker, but Im left with intermittent screen "shaking" up and down. Its very brief, but very annoying. It seems to happen the most during lots of action and at loading screens.
2) Crossfire on, in windowed mode. Same result as above.
3) Crossfire on, 16xAA. No flickering of any kind, but colors are very drab/washed out looking.
Im no expert with this stuff, so I apologize for my ignorance in overlooking something obvious.
Both video and motherboard drivers are up to date.
I doubt its causing your problems, but just so you know you are running 6gb of memory there (2GB video plus 4GB normal) on an operating system that can only address 4gb total...I have no idea how memory addresses are prioritised, but seems to be that theres a waste of components by using vista 32 instead of vista 64 with those graphics cards and that memory. No idea if it can cause problems as well...
try turning down the settings to on the standard settings tab just to balanced, and then give it ago.
i just tried maxing out all the settings in ccc before i loaded up left4dead and i got the save sorta thing, so give balanced a go, and then you can start experimenting from there.