Dual GPUs wasn't supported until Premiere Pro CC. You will probably need to undo the SLI, and may even need to physically remove one of the cards.
Unfortunately, Premiere Pro CS6 does not support SLI at all. It supports only a single GPU for CUDA acceleration.
In addition, CS6 (even with the 6.0.3 update) by default runs in software-only mode with a non-"certified" card such as your GTX 670 installed. You will need to edit the "cuda_supported_cards.txt" file to add the GTX 670 to that list in order to enable MPE GPU acceleration.
My thanks to those who have responded, much appreciated. Using one card is not an issue, Vegas Pro 12 does not support SLI either. I have a question for RjL 190365. You mentioned editing the "cuda_supported_cards.txt" file. Might sound like a stupid question but where would I find it. I used the Windows O/S search function with no luck. If adding the card to the file and was accepted things would be great if not then I might of wasted a lot of money. My thanks again and regards. Stewart
Your GTX 670 should work just fine.
You don't need to edit the cuda_supported_cards.txt file, simply rename it or delete it alltogether.
Windows search is lame!
You will find it in the following folder: c:\program files\adobe\adobe Premiere Pro CS6
Thanks Jim, I will play around with the GPU`s today, disable the SLI and if still no luck remove one card and will also find that file now I know where it is. I agree Windows search is lame. When I did my homework prior to purchasing the suite I did notice the NVidia 600 series cards were supported. Once again my thanks to you and the others for the help. Much appreciated, Stewart