I have a R290X and my ASUS motherbosrd is PCI-E 2.0 . I just installed the 15.7 update and I read that this will enable backwards compatibility . Will this also allow crossfire for PCI-E 2.0 .
1) Driver has nothing to do with PCI-E support.
2) 290X is PCI-E 3.0 capable card but will work on MB with PCI-E 2.0. I have already tested this with my AMD system.
3) CFX is a different story. Your MB has to support CFX. Just make sure what each card gets at least PCI-E 2.0 8x speeds per card.