I have read before that while using a GTX 660 Ti, although MSI afterburner will allow the user to "Unlock the voltage control", you aren't actually able to change your voltage with the slider; it just looks like you can. My voltage slider will let me go all the way up to +100 MV (To what base number I don't know). I've read about some things such as re-flashing the card's BIOS to a custom ROM that will allow me to actually change my voltage, but I don't want to do something I don't understand and get in over my head. After all, I am very new to overclocking.