I just bought a radeon 5850 and installed its most recent drivers. In every game I play, I get high frame rates but intense amounts of screen tearing. It doesn't seem to be stopped by turning on vsync. Could this be a monitor issue?
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where do you activate vsync? if you're doing it inside the game make sure the appropriate settings are set on CCC.
Or you can try install the older driver like 10.3 or 10.4, that's the most stable drivers for now...
You could try activating Tripple buffering but we really need to know the full specs and screen resolution to help properly.