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HoloDust on 19 April 2016
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Pemalite said:
HoloDust said:
Hm, I'm wondering what that GPU is, if that rumour is true...

PS4's GPU is either downclocked 7870 (Pitcairn) with 2CUs disabled, plus some additional circuitry from Hawaii, or it's downclocked 290 (Hawaii Pro) cut in half with 2CUs disabled.

So, this would be something like downclocked 290/390 with 4CUs disabled...or maybe it's Polaris based, which I doubt, but in any case I guess it needs to be on 14nm, 28nm would be too power hungry.

The PS4's GPU is close to a Radeon 7850.
This would put it near the Radeon 7970... At-least in terms of CU's.
We have no idea if it's using GCN 1.3 with it's colour compression or not, how many Texture Mapping Units or Render Output Pipelines or even if they bolstered the geometry units.
Way to many unknowns.

28nm is perfectly feasible, they will likely be aggressive with the voltages.
As a fabrication process matures you can tweak things for lower power consumption and more performance.

Performance wise, sure, numbers on the sheet are pretty similar to 7850. But it's 1280:80:32 chip with 2CUs disabled...I just don't know (nor was I ever able to find any info) is it Pitcairn XT with ACEs from Hawaii or is it Hawaii Pro cut in half (with 2 CUs disabled).

36CUs amount to 2304 shaders, which honestly sounds a lot like 40CUs (2560 shaders) of 290/390 cut down by 4CUs for better yields...so maybe 2304:144:64...which seems a lot to put onto 28nm if they want to keep TDP low.

I guess 28nm might be feasible if they're ditching PS4's design and going more toward the original PS3 TDP route...which I wouldn't be surprised honestly, if anything I was surprised by low TDP design of PS4 to begin with.