Vista + 2 different geforce cards

I have a GF8500GT and a GF8600GTS with Vista x64 and the CUDA 2.0 beta toolkit/SDK + the FW 174.55. The GF8500GT is connected to a display, the GF8600GTS not. I have no SLI bridge connected. Both cards are listed correctly in the Device Manager without any conflict. Only the 8500GT is used to display the Vista’s desktop.

For some strange reason the cudaGetNumDevices() retrieves only one device… the GF8500GT… the GF8600GTS is not listed by CUDA… Curiusly it is with Windows XP Pro x86 SP3… any idea why CUDA cannot see the 8600GTS in Vista, pls?


This is a known problem in the CUDA on Vista. See the announcements forum:
“- To use multiple GPUs, under Vista each additional GPU must have a desktop extended onto it.”

Eeeek! You’re right. It works if I extend the desktop to other monitor. I don’t know if that affects to the 5s watchdog … can I turn off the monitor connected to the GF8600GTS to avoid it then or not?


I’m doing some CUDA programming and my workplace has been kind enough to buy a very nice dual 9800 GX2 system (no, I don’t get to keep it, just to use it). I run Vista 64 both for technical reasons and political reasons.

After a fair amount of experimentation (and forum reading) I’ve been able to test a single GPU in 64-bit mode.

The problem is the [stupid] Vista bug where the desktop must be extended to the “other” 3 GPUs to get them recognized. Is there any way to extend the desktop onto these GPUs without having an attached monitor?