I have a standard VGA splitter connected to a nvidia nforce 631i on ubuntu 9.04. However, when the splitter is in use, the image gets dark. If I unplug one cable, it doesn't. this phenomenon is noted elsewhere on the net, but no solution.
I think this could be fixed by increasing the "power output" of the video card, which may involve overclocking or tweaking the voltage, but I know little about this.
I'm aware of powered VGA splitters, but I'm trying to make it work with the unpowered one I bought.