Thanks for the info. I understand all 7950s have 3gb of memory, will it still use just 3gb if I cross fire? If so, how do the extra frame rates happen?
Yes, if that is so then your 7950 will utilize the other 7950's memory if it has the same.
Crossfire works by a process called AFR. What that means is both cards work on alternate frames, hence 'AFR' - Alternate Frame Rendering. Basically one renders one frame and the other renders another and spits it back out on your screen.