Asus Nvidia GeForce GTX 680 Not rendering properly?

Hi, I am relatively new to 3D modding and rendering of images, I have an Asus Geforce Gtx 680 and it isn’t rendering anywhere near as fast as it should. My CPU redenders my image in 3 muntes and 43 seconds where as my GPU renders it in 8 minutes. My rig is GPU: GeForce GTX 680
CPU: Intel Core i7-477k @ 3.50GHz
Memory: 32 Gb (31.94 usable)
OS: windows 8.1 pro.
Could anyone advise me as to what to do to make it faster ???
Thank you,
Tom

Hi, most important for GPU is big tiles setting, try 256x256 in Render> Performance panel.
Try the benchmark file on GPU and set to 32x32 for CPU to compare.

http://www.blenderartists.org/forum/showthread.php?359492-The-new-Cycles-GPU-2-73-Benchmark

It would be nice if you add your render times to the last page.

Cheers, mib