I have a 6870 and I'm having an issue with Minecraft and my GPU clocks. I start up Minecraft and it stays at 300MHz for both core clock and memory clock. This causes huge texture loading issues. It seems to me as though the ATI drivers(I have 11.2) don't recognize Minecraft as requiring an increase in clock speed. Is there any way to either fix this or force the GPU clocks to gaming speeds?
I'm having a similar problem when I watch Youtube. If I turn Youtube on the memory clock goes up to 1050MHz like normal but if I start up a game with Youtube running the GPU core clock doesn't increase past 300MHz. Other than that it's only Minecraft. I suspect it's an issue with OpenGL and the ATI drivers.
Edit: I had this exact problem with my old card, a 5750. I also have a friend who has a 5770 and a 6870 and he has the exact same problem.