I have two GTX 770 graphics cards (Zotac and MSI, clocked the same) an SLI bridge, latest drivers and all that good stuff. I also have an Intel i5 4670k 16gb Ballistix Sports RAM, MSI z87-g45 gaming Mobo and 750w PSU. But, I get less frames with this SLI configuration than with only one card. Is the PSU a possible issue or the fact that the cards are different brands? Any response is appreciated, thanks