I read something about it being able to lower power usage when a video card is not being loaded. Can anyone comment on this? I am also debating ATI 4870 1GB vs. GTX 260 because the I heard the 260 uses a lot less power at idle/non gaming.
It works similar to the intel speed stepping. It downclocks the card to something like 500MHz when in idle to reduce the power consumption. I don't know anything deeper than that like what the % GPU load triggers are but in a nutshell, that is what it does.