Re: Power consumption GTS 250 versus GTX 240/260/275 with the Linux drivers?
As far as I know, basically it's quite tricky to change VRAM clock without switching off the display momentarily (causing flicker) if multiple outputs are used. I'm not sure why.
Point is, the GPU won't drop down into lower performance levels if multiple outputs are active.
I worked around this by modifying the BIOS to force every power level to the same, full VRAM clock. Be careful, your PC might crash and burn and you will lose your warranty.