i have a voltage locked 7950. While i cant directly change the voltage, there are certain thresholds present for the card to lower the voltage on it's own. kinda like when the card switches between 2d and 3d mode.

i think the card is stock @ 1ghz, and IIRC the card lowers the voltage @ 800mhz core (1.125v) and 600mhz (1.050v, i forget what it was honestly).

I haven't run into the need for this yet, but noticed it when playing with the settings.