I have 2 reference designed R9 290s in my rig (4790k, 32gb ram, Asus WS board). Since I updated to the 15.x drivers for the cards (Crimson), I been having issues with crossfire. When the machine starts up, both cards are on whereas only 1 used to be on. By on I mean that the secondary card is running at full clock with the fan on. The fix is to disable and re-enable crossfire it Catalyst, then it works properly until the system is shut down and restarted. Any ideas?