I made quite possibly the dumbest mistake anyone can make, so I doubt this is your problem, but I'll mention it anyway - the AMD Engine Control Center software has a Performance section where it's possible to set the speed that the card will run at. Regardless of what the bios is set to, it will always go by what the software is telling it to do, so if you have the "OverDrive" setting enabled and set to a low speed, the card will only operate at that speed. If that is enabled, disable it.