I'm trying out btc mining with 2 HD 6970 cards. Using AMD Overdrive Control, I have set core at 880 max, memory at 125 max, power at 0.930 max and fan speed at a linear control (about 46xx RPM when mining), temperature around high 70s low 80s C and getting around 280 MHash/sec each with Phoenix miner 1.50 and the following command
280 is too low. I also have two stock 6970 cards (haven't gotten around to playing with Overdrive yet), and I'm getting 350MHs each. I'm using LinuxCoin and poclbm without any switches except to identify which card (I was getting same results with Windows 7 & GUIminer before I switched to Linux).