Im going to build a computer in phases, starting out with a single 5770 and later adding on more. The card I had in mind initially was the Asus M4A79XTD EVO. The problem(?) is that while youll get the 16x speed on the pci express bus with one card, youll only get x8 with two. Do you think this will affect the performance at all?
I will use 4g ram and a amd phenom II x4 965 cpu with this setup.
Yes there is a negative affect on performance, but it is pretty small. Even so, the additional cost of 790FX boards over 790x/790GX boards is low enough now that you may just want to go with a 790FX based board. For a midrange card in crossfire like the 5770, the difference may only be 5%, but it will probably be a greater difference if you want to use eyeinfinity.