Soleron on 24 November 2012
http://en.wikipedia.org/wiki/Comparison_of_Nvidia_graphics_processing_units
http://en.wikipedia.org/wiki/Comparison_of_AMD_graphics_processing_units
Rough approximation, performance = shader count * clock speed * prefactor
The prefactor is different between pre-5000 AMD cards, post-5000 AMD cards, and Nvidia cards.
