GPU Performance

All of our discussions around the new iPad and its silicon thus far have been in the theoretical space. Unfortunately the state of Android/iOS benchmarking is abysmal at best today. Convincing game developers to include useful benchmarks and timedemo modes in their games is seemingly impossible without a suitably large check. I have no doubt this will happen eventually, but today we're left with some great games and no way to benchmark them.

Without suitable game benchmarks, we rely on GLBenchmark quite a bit to help us in evaluating mobile GPU performance. Although even the current most stressful GLBenchmark test (Egypt) is a far cry from what modern Android/iOS games look like, it's the best we've got today.

We'll start out with the synthetic tests, which should show us roughly a 2x increase in performance compared to the iPad 2. Remember the PowerVR SGX 543MP4 simply bundles four SGX 543 cores instead of two. Since we're still on a 45nm LP process, GPU clocks haven't increased so we're looking at a pure doubling of virtually all GPU resources.

GLBenchmark 2.1—Fill Test

GLBenchmark 2.1—Triangle Test (White)

GLBenchmark 2.1—Triangle Test (Textured, Fragment Lit)

Indeed we see a roughly 2x increase in triangle and fill rates. Below we have the output from GLBenchmark's low level tests. Pay particular attention to how, at 1024 x 768, performance doubles compared to the iPad 2 but at 2048 x 1536 performance can drop to well below what the iPad 2 was able to deliver at 10 x 7. It's because of this drop in performance at the iPad's native resolution that we won't see many (if any at all), visually taxing games run at anywhere near 2048 x 1536.

GLBenchmark 2.1.3 Low Level Comparison
  iPad 2 (10x7) iPad 3 (10x7) iPad 3 (20x15) ASUS TF Prime
Trigonometric test—vertex weighted
35 fps
60 fps
57 fps
47 fps
Trigonometric test—fragment weighted
7 fps
14 fps
4 fps
20 fps
Trigonometric test—balanced
5 fps
10 fps
2 fps
9 fps
Exponential test—vertex weighted
59 fps
60 fps
60 fps
41 fps
Exponential test—fragment weighted
25 fps
49 fps
13 fps
18 fps
Exponential test—balanced
19 fps
37 fps
8 fps
7 fps
Common test—vertex weighted
49 fps
60 fps
60 fps
35 fps
Common test—fragment weighted
8 fps
16 fps
4 fps
28 fps
Common test—balanced
6 fps
13 fps
2 fps
12 fps
Geometric test—vertex weighted
57 fps
60 fps
60 fps
27 fps
Geometric test—fragment weighted
12 fps
24 fps
6 fps
20 fps
Geometric test—balanced
9 fps
18 fps
4 fps
9 fps
For loop test—vertex weighted
59 fps
60 fps
60 fps
28 fps
For loop test—fragment weighted
30 fps
57 fps
16 fps
42 fps
For loop test—balanced
22 fps
43 fps
11 fps
15 fps
Branching test—vertex weighted
58 fps
60 fps
60 fps
45 fps
Branching test—fragment weighted
58 fps
60 fps
30 fps
46 fps
Branching test—balanced
22 fps
43 fps
16 fps
16 fps
Array test—uniform array access
59 fps
60 fps
60 fps
60 fps
Fill test—Texture Fetch
1001483136 texels/s
1977874688
texels/s
1904501632
texels/s
415164192
texels/s
Triangle test—white
65039568
triangles/s
133523176
triangles/s
85110008
triangles/s
55729532
triangles/s
Triangle test—textured
56129984
triangles/s
116735856
triangles/s
71362616
triangles/s
54023840
triangles/s
Triangle test—textured, vertex lit
45314484
triangles/s
93638456
triangles/s
46841924
triangles/s
28916834
triangles/s
Triangle test—textured, fragment lit
43527292
triangles/s
92831152
triangles/s
39277916
triangles/s
26935792
triangles/s

GLBenchmark also includes two tests designed to be representative of a workload you could see in an actual 3D game. The older Pro test uses OpenGL ES 1.0 while Egypt is an ES 2.0 test. These tests can either run at the device's native resolution with vsync enabled, or rendered offscreen at 1280 x 720 with vsync disabled. The latter offers us a way to compare GPUs without device screen resolution creating unfair advantages.

Unfortunately there was a bug in the iOS version of GLBenchmark 2.1.2 that resulted in all on-screen benchmarks running at 1024 x 768 rather than the new iPad's native 2048 x 1536 resolution. This is why all of the native GLBenchmark scores from the new iPad are capped at 60 fps. It's not because the new GPU is fast enough to render at speeds above 60 fps at 2048 x 1536, it's because the benchmark is actually showing performance at 1024 x 768. Luckily, GLBenchmark 2.1.3 fixes this problem and delivers results at the new iPad's native screen resolution:

GLBenchmark 2.1—Egypt (Standard)

GLBenchmark 2.1—Pro (Standard)

Surprisingly enough, the A5X is actually fast enough to complete these tests at over 50 fps. Perhaps this is more of an indication of how light the Egypt workload has become, as the current crop of Retina Display enhanced 3D titles for the iPad all render offscreen to a non-native resolution due to performance constraints. The bigger takeaway is that with the 543MP4 and a quad-channel LP-DDR2 interface, it is possible to run a 3D game at 2048 x 1536 and deliver playable frame rates. It won't be the prettiest game around, but it's definitely possible.

The offscreen results give us the competitive analysis that we've been looking for. With a ~2x die size advantage, the fact that we're seeing a 2-3x gap in performance here vs. NVIDIA's Tegra 3 isn't surprising:

GLBenchmark 2.1—Egypt—Offscreen 720p

GLBenchmark 2.1—Pro—Offscreen 720p

The bigger worry is what happens when the first 1920 x 1200 enabled Tegra 3 tablets start shipping. With (presumably) no additional GPU horsepower or memory bandwidth under the hood, we'll see this gap widen.

The Impact of Larger Memory A5X vs. Tegra 3 in the Real World
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  • PeteH - Wednesday, March 28, 2012 - link

    No idea. Was it necessary to upgrade the GPU to get an equivalent experience on the larger screen in that case, or was performance on the 3GS limited by the CPU (or RAM, or something else)? Reply
  • zorxd - Thursday, March 29, 2012 - link

    just look at benchmarks on this web site

    The iPhone 3GS gets more FPS in 3D games because of the lower resolution.

    So in short, yes, it would have been necessary to upgrade the GPU to keep the same performance.

    But no matter what Apple does, people will always say it's the right choice.
    Reply
  • PeteH - Thursday, March 29, 2012 - link

    I looked for a comparison between 3GS and 4 game FPS comparison and couldn't find anything. Can you point me to it?

    I'm looking for hard numbers because just increasing the resolution doesn't necessarily mean a GPU upgrade is necessary. If (and this is completely hypothetical) the 3GS was performance limited because of its CPU, improving the CPU in the 4 could allow it to achieve the same performance at a higher resolution.

    I'm not remotely saying this is the case, just that I've seen no numbers demonstrating a drop in frame rate from the 3GS to the 4.
    Reply
  • dagamer34 - Friday, March 30, 2012 - link

    I believe the GPU got a clock speed increase when it went from the 3GS to the 4. Reply
  • Peter_St - Monday, April 02, 2012 - link

    Oh wait, let me rephrase this: I have this nice shiny tower with 2GB of RAM and newest CPU out there but shitty OS with java hogs and memory leaks, but who cares, I'll just go and jerk off on the specs.

    I think that's what you wanted to say...
    Reply
  • tipoo - Wednesday, March 28, 2012 - link

    GPUs which consume hundreds of times more watts than SoCs like this and have much more memory bandwidth at their disposal still struggle with the resolution this thing is displaying. The Xbox 360 GPU has, if I recall, around 25GB/s vs 6 in this, and that struggles to run games at 720p in a constant 30FPS. So far, it seems like the retina compatible games do display at native res, but there aren't any improvements in textures, effects, etc. So would the additional GPU power effectively be negated by the resolution for native apps, and still be constrained to games that look straight out of 2003-4? Or is Imagination Tech's video memory compression that much more advanced than AMDs/Nvidias so bandwidth doesn't matter as much? Reply
  • zorxd - Wednesday, March 28, 2012 - link

    It's not only about the resolution. You could probably play Doom just fine with the SGX543MP4 at this resolution. The problem is when you have more complex level of details, shaders, etc. The iPad couldn't play a game like Crysis even at half resolution. But even at 2048x1536, Doom will still look like a game of the 90s. Reply
  • tipoo - Wednesday, March 28, 2012 - link

    *12.8GB/s, my mistake Reply
  • BSMonitor - Wednesday, March 28, 2012 - link

    What's battery life watching a bunch of movies.. say from New York to Hawaii? Will I be able to get 9 hours??

    Can run all the compute benchies we want, but primarily these are portable entertainment devices. The simplest use being the most common.
    Reply
  • PeteH - Wednesday, March 28, 2012 - link

    Depends how bright you want the display, but from the number they're posting you should be fine at < 70% max brightness.

    I would argue that the most common use case is probably web browsing though, not movie watching. Unless... how often are you on these flights from New York to Hawaii?
    Reply

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