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Conversely, I've been running crossfired 5850s for over a year now with not problems at all.
I'd say that's a VRAM issue. With my 1GB 5770's, I had to make sure I closed any YouTube pages I had open before I tried playing BF3 on high, as leaving any kind of flash video open in my browser pushed my VRAM usage right too the limit and knocked my fps down from ~52 to ~34 FPS. Playing on a GTX 470, 570 and 480, I didn't have this issue.Okay but like I said, most games have performed well, its BF3 that gives me issues, any of you guys running BF3 and can clarify how it performs? I.e. you running ultra settings? constant 60 fps on high details? etc....
I'll play 2 games over a day, the first 64 player for example on lets say caspian, runs perfect, fluid 55-60 fps constant.. Lovely.
Play a game a few hours later on a diff server with similar ping, same players same map... 30-40 fps.
Pc hasn't had anything changed, running exactly the same, just sat there in between maps so nothings changed config wise, yet performance is 1/2 of previous game. Its this inconsitency that drives me crazy.