I have 2 7950s in Crossfire. GPU 1 remains constant, but GPU 2 will fluctuate randomly and very quickly between ~500Mhz and 950Mhz. Just standing there looking at the wall and it keeps jumping around like that. Temps are under 60*C so it's not thermal throttling. PSU is Thermaltake 850W Smart Series. I haven't had this issue in any other games.