Seems this isnt working properly for me, unless its changed by design. So expected behaviour based on all my old nvidia gpu's, is that when this option is selected the gpu clock speed will never fall below base 3d speed (typically somewhere in the mid to high 1000mhz range.), the benefit of this option is for older games where the gpu is overpowered so it falls down to 2d clocks, but then this causes stutters as 2d clocks wont be enough to run game smoothly, so typically in these games the gpu can have a problem of looping between 2d and 3d clocks, which "prefer max performance" fixes. I noticed when playing fable anniversary if I use optimal performance its not that bad but it isnt perfect, e.g. game stutters when exiting menus as it has to get out of idle clocks, so I tried prefer maximum performance, and its going down to 2d clocks, and not only going down it seems to do it a lot, the game was a stutter fest. I think its a bug, as I have owned many previous gen cards and they never had this behaviour. But curious if anyone else has noticed this, note its probably not going to be an issue in modern games which load up the gpu, also if people are not capping framerate.