I need to decide between two graphic cards at the moment. One card has 2GB Ram (ATI), the other has about 1,3GB (nVidia). I want to use it mainly for interactive pathtracing rendering with OpenCL. Now I am wondering if the performance of the 570 GTX is going to be slower than the performance of the 6970. In general the performance of the 570 GTX is a little bit higher, but what about OpenCL? Will I benefit a lot from mor memory? Unfortunately 99,9% of all graphic card reviews do not cover OpenCL performance. Which card would be more suitable for my needs?
I can’t comment on which GPU will be better for this task but look at the card with the most memory bandwidth and largest caches. Path tracing on real-world scenarios is heavily bandwidth bound due to its stochastic nature.