In many recent NVIDIA GPUs shipping in graphics cards, the FP64 cores are executed at reduced speed. For example, the GTX Titan is capable of achieving a
double performance that is 1/3 of
float performance. However, by default the card does FP64 at a reduced speed of 1/24 of FP32. This is done because the primary audience of these consumer cards are gamers. And games use mostly FP32 computations. Enabling full speed FP64 reduces the FP32 performance by a bit since the maximum clock speed needs to be reduced and also increases power consumption since all the power hungry FP64 cores are running.
To enable full speed FP64 on Linux, make sure you have the latest NVIDIA drivers installed. Open the
NVIDIA X Server Settings application. Go to the section with the name of your graphics card > PowerMizer and enable the
CUDA - Double precision option. That is it, your CUDA application should now run with full speed FP64 on the GPU.
Tried with: NVIDIA GTX Titan, NVIDIA driver 319.37, CUDA 5.5 and Ubuntu 12.04 LTS