CPU: Intel i5-3470 3.2Ghz
GPU: Nvidia GTX 960
OS: Windows 10 64bit
Yea, I got a pretty old system here. Here is my time:
Best Time: 2 min 10 seconds (GPU - CUDA)
Best Time: 6 min 40 sec (CPU)
GPU
64 X 64 - - - - - - - 04:17
128 X 128 - - - - - 02:40
256 X 256 - - - - - 02:12
512 X 512 - - - - - 02:10 
1024 X 1024 - - - 02:23
CPU
64 X 64 - - - - - - - 06:40
128 X 128 - - - - - 06:44
256 X 256 - - - - - 07:40