If you cannot make it work, it might worth a try:
http://forum.ethereum.org/discussion/9443/bricked-your-rx-480-due-to-bad-flash
http://forum.ethereum.org/discussion/9443/bricked-your-rx-480-due-to-bad-flash
Thanks for help spiz0r, i cant't understand if it is a sort of brick, only the asus detect the card and only if connected to pcie, asrock z97 anniversary and asrock h81m btc doesn't detect it and how possible the problem remain also after i restore the original bios backup of 470
You are right, it is really strange if it works in at least one motherboard.
Just to make it clear, if you put it in any other motherboard, it doesn't even start, right? You just have a black screen.