is there a document somewhere on which SLI/crossfire configs work? some are reporting it doesn't, across both nvidia/ati select models.
or do we have to troll forums for that info? would be nice if someone could collect all the info (not customers/forum users to be precise)...
specifically 7870.
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actually, a bit on the vsync reducing stutter you mentioned. if you wanna know the trick/key it's this:
run 40 fps. make sure it never drops below 30. if it does, vsync will skip 2 frames... running at 45 will skip every 3rd frame (draw 2, skip 1)... pretty simple logic on how vsync works. skipping 1 frame is ok, skipping 2 is problematic.
although the stutter you mentioned is probably related to screen tearing with vsync off. running with vsync off when you frame rate is below your refresh rate (with double-buffer) is horrible. so yea ;p
vsync is a 'frame-skipper' basically. prevents drawing partial frames so you don't get screen tearing at frames below refresh.