I recently installed a few dual-GPU CUDA workstations (two dual gtx480s and a dual gtx470) with no apparent trouble. I just tried a gtx480/ Tesla C2050 and not only does deviceQuery fail with a weird error - something about an invalid device ID or count or something - but now the machine won't boot into graphical mode (remote access via ssh still works fine). I assume I am doing something tragically wrong... Is mixing these GPUs even possible? If so, does it require special configuration? I must have missed something basic. Any help is appreciated - I am new to this and need all the help I can get.
Sorry, I thought I mentioned the OS. It's 64-bit CentOS 6, based on RHEL 6. The error is "invalid device ordinal" or some such. Imm going to try a few things and get back with more info, but I appreciate the suggestions so far, and will try migrating to superuser or unix... Thanks!
So, in desperation, I tried reseating the Tesla C2050. Guess what? I only had one of the two power connectors in (!). Weirdest thing was that although it showed up fine with lspci and every other way I could check it, it was causing X to fail and deviceQuery to crap out. I guess the moral of the story is that I need to be less of a muppet. If anybody else is having the same problem... something to check!