PCIE 2.0 x16 or x4 for Crossfire?

blacklex

Honorable
Apr 7, 2013
147
1
10,690
Ok, I am very new to this computer building things and I am not sure on how to approach this one problem. I am planning on getting a 7770 and in the future maybe having a crossfire system. My only question is, what is the difference between x16 and x4? Will there be a performance drop?