My 4650 alternates between 0.9V (low power) and 1.25V (high power). Yours should also downclock/undervolt when it is in 2-D or doing nothing. I have noticed sometimes the info programs will increase the load on components making them clock up to their higher speed. Does it just sit at 1.25V? If it does, make sure you have the newest drivers (and maybe any windows power options set to balanced).