
Apple A8X’s GPU – GXA6850, Even Better Than I Thought - shawndumas
http://www.anandtech.com/show/8716/apple-a8xs-gpu-gxa6850-even-better-than-i-thought
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cromwellian
Seems like they're pulling a GeForce FX in some ways though, using FP16 in
shaders in benchmarks. The GFXBench PSNRs seem to suggest 50% worse than
Maxwell.

NVidia was raked over the coals in the GeForce FX era for running FP16 shaders
because FP32 ran far slower (ATI was using FP24 which was a nice sweet-spot at
the time)

I'd like to see more image quality comparisons for mobile GPUs like the
Desktop Era, because there may be cheating involved in IQ department.

Also, in comparisons with the K1, keep in mind NVidia claims K1 is DirectX12
class, so some of the die space is being used for functionality not benched in
GFXBench.

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jra101
In OpenGL ES there is no default precision in the fragment shader.
Applications must explicitly specify the minimum precision as highp (FP32),
mediump (FP16), or lowp (10 bit integer).

If the application uses mediump or lowp the GPU is free to run those
computations at a lower precision.

[https://developer.apple.com/library/ios/documentation/3DDraw...](https://developer.apple.com/library/ios/documentation/3DDrawing/Conceptual/OpenGLES_ProgrammingGuide/BestPracticesforShaders/BestPracticesforShaders.html#//apple_ref/doc/uid/TP40008793-CH7-SW7)

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cromwellian
Yes, but it's still apples-to-oranges. If drivers are defaulting to lower
precision, you're essentially comparing two different workloads.

(I'm not sure why people are voting it down, it is a legitimate point to want
to see Apples-to-Apples benchmarks. GFXBench has a high-precision Render
Quality bench, but it doesn't appear to have a high-precision framerate
benchmark)

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Xoxox
Got to wonder where it will be when Maxwell goes 20nm and maybe others got new
architectures soon..Sure they can afford to use much bigger SoCs than others
since they make their own but it doesn't seem all that efficient. In the end
we measure mobile GPUs by perf in synthetic benchmarks and that has no real
relevance since all wee need is for games to run well.Wish mobile benchmarking
would get better tools already since GPU testing is rather misleading and we
all look for best perf not good enough perf.

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rsynnott
This seems rather like the A5; a slightly custom job, using off the shelf core
designs. It'll be interesting to see what the A6/Swift equivalent is like in a
year or so...

