I installed CUDA 4.0 and after a while I got fallowing error:
gkokosinski@cuda2:~/kmeans$ nvidia-smi -q
NVIDIA: could not open the device file /dev/nvidia2 (Input/output error).
Nvidia-smi has failed because your system has at least one NVIDIA GPU that is insufficiently
powered. This may be because not all required external power cables are attached, or the attached
cables are not seated properly.