Ubuntu does not detect nVidia's second GPU

Question

I have 2 GPUs installed on my system: GTX660 and 880GTS. Both are detected and work fine under Windows 8, and Ubuntu 12.04 is 32 bits.

Now I installed Ubuntu 12.04 64bits on the same system, with the latest drivers from nVidia (304.64 in 64 bit). In console mode (CTR + ALT + F1) I can detect and use both cards (through, for example, the CUDA application).

In X-mode (I use the standard lightdm server), only the GTX660 only detects the same application. Running lspci from the X-terminal shows both GPUs (the GTX660 is called “VGA-compatible”, while the 8800GTS is clearly labeled on equal terms).

It seems to me that I'm more connected with the X server.

Any idea how to fix this?

Answer 1

The problem is resolved - but I'm not 100% sure why.

In the meantime, I changed the grub configuration (see here ) by adding the nomodeset attribute to GRUB_CMDLINE_DEFAULT since I could not access the console.

Since then, the problem seemed to be resolved, i.e. now I can see my two GPUs even in X.

ls -l /dev/nvidia* returns both devices and the controller.

Thanks for your ambulance!