Good thread. I'll have to link it to my comparison thread and likely update some stuff. Its been too long since I last edited it.

I heard some details before when there was some talk about yield problem of Xbox GPU, which is like PS4 and Xbox will have 20 and 14 Computer Units instead of 12 and 18 but two of them will be used for yield problems, so Sony might be trying to use these spare two units due to some good yields. I'm not sure about this just wanted to let you know.

GCN is 28nm that means xbone is also 28nm. 40nm would be a gigantic die for xbone the 40nm was a mistake. Xbone is definetly 28nm.

That is not what he means. He probably had something similar (or slightly higher) in mind, like 12 or 14 CUs. It would have been enough for 1080p as Forza/MS has shown (every CU more on your die increases tdp and size=costs so both Sony/MS went for minimal die size to get the job done). However, after (probably endless) simulations, he realised that with <=14 CUs, things could get too tight when adding gpgpu tasks. With 18 CUs, simulations showed there is enough raw power to get 1080p done, and have good breathing room for gpgpu stuff running concurrently.

Corrected to 28nm.

I agree, no console needs plutonium-powered 1.21 Gigawatts of power. ;)

On serious note, when some people around here start claiming that WiiU is 1/2x XOne and 1/3 PS4 (4770-4850 performance), for which you would need something close to 896:48:16 VLIW5 GPU at WiiU's clock of 550MHz, which at 40nm fab is bigger than the whole WiiU's GPU package, let alone area reserved just for GPU (minus eDRAM and the rest)...well, making BttF jokes is really mild overreaction compared to alternatives.

BTW, WiiU's GPU, when you look at rumored SPU:TMU:ROP count and GFLOPS/fill rates is a perfect match with 5550, not 4670.

Putting in "More than needed" is a decades old engineering solution to get redundancy into dies (a few more memory cells in caches, a few more graphics units in the gpus. Just how many more is a difficult arbitration between ecpected waver defect rate and increased costs due to more die space). The Cell has one entire SPU for redundancy. And no, neither Sony nor MS will ever use more than the 18/12 CUs, because that is the very point of consoles: you have one fixed, constant forever pool of resources.

Thanks for the info, you're correct. I did go through the architecture of 5550 and its indeed a perfect match than previous one. I've updated the post with the details of Wii U GPU in specifications and architecture.

UPDATE: Xbox GPU info updated