I have a small rig with AMD cards but I also mine on my desktop PC when I'm not using it. I have a GTX 960 in it. When mining the computer is pretty much unusable with terrible input lag, the mouse pointer barely moves and doing anything else on it is about impossible.
However, on AMD rigs the computer can be mining but there is still usually enough function of the PC left to able to browse the web, read email etc.
Why is this and is there any way to make a nvidia rig more functional while mining?