What\'s the difference between running CrossFire on x8/x8 and x16/x16?

[tyler howlett]

i have 2 7850s and i am not getting the amount of performance i should be getting so i was wondering if it was my motherboards fault and if i should upgrade to a new one? my mother board is an asus p8h77-v le and it has on slot at pci 3.0 x16 and the other at pci 2.0 at x4. i was think that this could be aproblem but i am not sure so can ayone help me with my performance issues.

 

[rolli59]

16/16 versus 8/8 is almost no difference http://www.techpowerup.com/reviews/Intel/Ivy_Bridge_PCI-Express_Scaling/23.html
Average 10% performance loss using 16/4 versus 8/8 http://www.tomshardware.com/reviews/pci-express-scaling-p67-chipset-gaming-performance,2887-10.html