I'm trying to get output on my secondary videocard, but it remains black.
My system has a geforce 8800gtx and a 7100gs, running the 182.08 driver on windows XP. When I hook up a screen to the 7100, resolume outputs nothing to it, output to the secondary 8800 screen works fine.
I tested dragging some game windows onto the 7100 from the 8800 without any performance loss, which leads me to believe it can be used as an extra output for the 8800, without using its own slow chip at all. These were however direct3d applications, so I don't know if this same functionality can be found in opengl.
I previously tested the same with a 7800gtx as secondary videocard, rendering the same results.