Technically sins takes advantage of two kinds of processors:
a CPU and a GPU.
The increase in graphics seen in Rebellion is primary handled better with a GPU as opposed to central processing.
Currently the devs offload the load on-to the GPU so they only require 1 cpu core handling key functions of the iron Engine running the game.
I suppose one could go so far as calling it cheating since GPU's have become so godlike in paralleled processing power.
Keeping your CPU at very low temperatures and overclocking it will see an improvement in the games performance up to the point where speed is not necessary. This limit is unknown but beyond that limit means the devs could add cpu processed features to enhance the game.
Rumors say: 4.5ghz