That motherboard has a pci-e 3.0 16x slot and a pci-e 2.0 4x slot.
It's generally not recommened to run x-fire with that setup, however it will still work, the 2nd card will be crippled by that slot.
IIRC the 4x slot runs through the chipset, this will add extra latency to x-fire, you may see worse then normal frame times (Someone will correct me if im wrong).