Are you and the Doc using 4 GPU clients, with no dummy plug or second monitor? You say you are not using the -forcegpu flag...I thought that flag was required if you were not to use a dummy plug or second monitor, and have SLI enabled (as per my post here:
http://www.hardwarecanucks.com/foru...sli-enabled-no-dummy-plug-second-monitor.html )
I don't run 4 gpus on a machine to be able to help here a whole lot. I have only ever had to deal with two clients.
On that note, does anyone know if it is possible for there to be a wonky core or such on a card and have the SLI to work still? Is it possible that when kruzn games, he is gaming on three cores and not four?
If it is possible that a core is not working, or your setup prevents you from using 4 cores at a time for some reason (if the problem moves from cores 3 and 4), can you run a temperature testing program to track the temps of all four cores, and then try a game with SLI enabled.
My theory is that if he enables SLI, and plays a game, and all four GPUs work, the temps should rise on all GPUs...no? If he games, and the temps stay the same on one core, but rises on the other three, then one core is not being engaged?