Re:Apple A8X’s GPU – GXA6850, Even Better Than I Thought
by jra101 on Wednesday November 12, 2014 @02:54PM
(#8597742)
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...
Re:Apple A8X’s GPU – GXA6850, Even Better Than I Thought
by cromwellian on Wednesday November 12, 2014 @11:04PM
(#8599854)
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)
Re:Apple A8X’s GPU – GXA6850, Even Better Than I Thought
by jjoonathan on Wednesday November 12, 2014 @04:54PM
(#8598492)
Hey, at least they aren't FP8s (no, I'm not kidding -- I had to get a shader demo working 6 or 7 years ago and I encountered some verrry strange rounding behavior on an intel GPU that I eventually traced back to this fantastic little "feature").
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.