I believe in practice register renaming (http://en.wikipedia.org/wiki/Register_renaming http://en.wikipedia.org/wiki/Register_renaming) largely negates the diff

I believe in practice register renaming (http://en.wikipedia.org/wiki/Register_renaming http://en.wikipedia.org/wiki/Register_renaming) largely negates the difference in performance. Notice the mention of some CPUs having MORE registers than are nameable in the instruction set. I am not a hardware engineer though, so YMMV.