I had the problem of getting CUDA to see my second GPU as I have only 1 monitor. There’s a solution posted on the Folding@Home nVidia forum which I tested and it works great.
However, I would like to hear peoples comments on the solution below.
Could it damage the cards TV decoder chip or worse?
Basically under Vista x64 CUDA won’t see your second card unless SLI is disabled and you have a second monitor attached to it.
So the fudge is to connect the composite TV-outs from both of your cards back to back. Once you restart your system, go into the Display control panel applet and extend your display out to the third monitor (first port on second card).
This will be greyed out and probably at a default resolution of 640x480.
Once you enable and apply it, it should stay enabled.
It basically fools Vista into thinking you have a TV connected to both cards as extra displays.
Now run any of the CUDA MultiGPU tests and you should get…
CUDA-capable device count: 2, and all the MultiGPU stuff should work perfectly