Quote Originally Posted by Macadamia View Post
^ Evergreen had OCP so Furmark didn't use more than board power.

WXYZT turns to WXYZ with T probably done in emulation (WXYZ or T for GPGPU).
The penultimate reason for this is die size. And yet Cayman is still big. Makes you wonder.
I disagree about die space. Reducing the width of the SP increases the ratio of logic per SPU. Without knowing more specific architectural details I'd guess 5D->4D is ambiguous or detrimental to die space.