Hello! I was wondering if it will work fine running Crossfire with 1 hd 7970 asus matrix platinum and 1 hd 7970 with ghz bios.
The matrix has stock voltage approx 1,185V and the sapphire has app 1,132V. I can syncronize the core clocks but the memory clocks wont sync. Stock mem clocks is matrix 1650 and sapphire 1500. Will this be a problem?

And one more thing. How much system ram do I need to get max performance in crossfire mode? I only use 4gb now and I noticed considerable lower fps in bf3(in crossfire) when I went from 8 to 4 gb. (found out one stick was broken)