Asrock z77 pro3 Crossfire?

[AwesomeSauce]

So i would like to ask if it's possible to use crossfire on this motherboard.
What can happen when i use crossfire one HD7850 on PCI-E 3.0 and another one on PCI-E 2.0

 

[alexoiu]

From the manual:
PCIE2 (PCIE 3.0 x16 slot) is used for PCI Express x16 lane width
graphics cards, or to install PCI Express graphics cards to support
CrossFireXTM.
PCIE3 (PCIE 2.0 x16 slot) is used for PCI Express x4 lane width graphics
cards, or to install PCI Express graphics cards to support CrossFireXTM.

In CrossFireXTM mode, please install the PCI Express x16 graphics
cards on PCIE2 and PCIE3 slots. Therefore, PCIE2 will work at x16
bandwidth, while PCIE3 works at x4 bandwidth.

I wouldn't use Crossfire on this board. I don't think that the gain in performance would justify the cost.