Also the 3d performance argument is bullshit, it's pure penny pinching. Bruno showed that their 2d core takes 26k transistors, including VGA bios which is also included in AMD cards still. Current manufacturing puts around 9M transistors per mm^2.
So a 2d core would take the __huge__ amount of space of 0.0028 mm^2, or 2800 um^2. That's a rounding error in a chip of 440 mm^2.