Rasterizer
Member
- Aug 6, 2017
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he stated as fact that there are several disabled features that are performance enhancing. I just want proof of his statement
Providing good evidence that enabling NGG fast path in Vega drivers should provide a significant performance uplift is pretty straightforward: People have spent years talking about how Fiji was a fundamentally flawed GPU design that was severely front end bottlenecked, and that this is why it struggled against the 980ti. Vega, as it currently stands on the newest public driver, is at least as front end bottlenecked by culled geometry performance as Fiji was, as it is currently realising an identical ~3.75 triangles per clock of culled geometry throughput:
(Incidentally, the numbers given her for list culled geometry performance exactly match the Fiji and Vega native pipeline numbers from the Vega whitepaper). That Vega is, in practice, front end bottlenecked is also easily confirmed by noting that Vega 56 performs 100% the same as Vega 64 at the same clocks despite having 8 less CUs.
The Vega whitepaper claims that primitive shaders are able to significantly increase front end culled geometry throughput prior to any fixed function culling (of the type done in Polaris with the Primitive Discard Accelerator) from 4 triangles per clock to up to 17. If even half of this claimed gain was actually realised by implementing primitive shaders, this would literally double Vega's culled polygon throughput and should substantially alleviate Vega's front end bottleneck, allowing Vega to much more readily keep its shader array fully saturated.
Unless you intend to claim that the feature doesn't exist that RTG simply made it up in the whitepaper, or that Fiji wasn't extremely well known to be front end bottlenecked by its geometry performance and that doubling (or more!) Fiji's culled geometry performance wouldn't have substantially increased its performance in games, I don't see how you can claim that doubling (again, or more) Vega's culled polygon throughput won't substantively increase Vega's performance in games.