ethomaz on 16 November 2013
I know... I know... people will say these are for redundancy but..
PS4's APU have 20 CUs intead 18 CUs... Sony for now choose to disable two of them.
It is unlikely that Sony will enable these two CUs in future but it is possible using a simple firmware update.
http://wccftech.com/ps4-apu-apparently-128-hidden-stream-processors-10-power/
