Added 2nd identical 5770 and I'm getting worse performance than a single card running in X4. Uninstalled all ati drivers, installed 10.2 (tried 10.3 later also). I tried a stronger power supply (750w +12V@60A) and no luck. Am I missing anything? Any suggestions? I read you can expect a 5% performance loss with PCI-e 2.0 x16 / x4 crossfire, is that a loss over a single card in x4 or two in x16?