Early 2016 Look: OpenCL & CUDA Comparison On 13 NVIDIA GPUs
A nice look at how the OpenCL performance compares from a GeForce GTX 650 Kepler to GTX TITAN X Maxwell with the open-source JuliaGPU.
And the results for the very popular LuxMark... The performance-per-Watt and performance-per-dollar results follow on the later pages.
It's to no surprise that the GTX TITAN X and GTX 980 Ti dominate the less expensive and older NVIDIA siblings.
Thanks to the automation of the Phoronix Test Suite, you can easily see how your own hardware compares to these results.