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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  • sjael - Wednesday, March 28, 2012 - link

    On the 'A5X vs Tegra 3 In the Real World' page, you mention Modern Warfare 3 as a iOS+Android game.

    I think, since I haven't seen this game ported to phones/tablets, you *might* be thinking Modern Combat 3.

    And then of course you show the market page for it further down..
    Reply
  • Anand Lal Shimpi - Wednesday, March 28, 2012 - link

    Correct - thanks for the heads up!

    Take care,
    Anand
    Reply
  • Celestion - Wednesday, March 28, 2012 - link

    Looks like the 3rd gen iPad was CPU limited in that first GlBenchmark test. Reply
  • Anand Lal Shimpi - Wednesday, March 28, 2012 - link

    That would be vsync :)

    Take care,
    Anand
    Reply
  • Celestion - Saturday, March 31, 2012 - link

    I see. Thanks! Reply
  • Kevin G - Wednesday, March 28, 2012 - link

    Memory bandwidth tests just seem to be off for what you'd expect a quad channel 128 bit wide memory bus to perform as. Performance didn't move from the dual channel 64 bit wide bus in the iPad 2. Could there be a software bug (Geekbench or iOS) limiting performance there? It'd be nice to revisit the memory tests after the next major revision of iOS and in conjunction with a later release of Geek Bench.

    Any chance of getting the exact resolution that Infinity Blade 2 runs on the rev 3 iPad? I'm assuming it'd be either 1536 x 1152 or 1368 x 1024 for quick scaling purposes.
    Reply
  • slashbinslashbash - Wednesday, March 28, 2012 - link

    They addressed this in the article.

    "It would appear that only the GPU has access to all four channels." - Page 12

    The GPU is hooked up to the RAM controllers. The CPU communicates to the RAM through the GPU. The GPU gets all 4 channels, the CPU only gets 2. The benchmark measures CPU-RAM bandwidth, not GPU-RAM bandwidth.

    It's actually kind of interesting, as it's an inversion of the typical architecture that we're all used to from PCs. But it makes sense, since the new iPad is basically a very nice screen with a smartphone CPU attached. The very nice screen requires a very nice GPU to drive it, so the GPU is more important (and would be memory starved with only 64 bits). The CPU just has to be "good enough" while any shortcomings in the GPU would be magnified at this resolution.
    Reply
  • tipoo - Wednesday, March 28, 2012 - link

    Which way is the PS Vita configured? That has the same quad core GPU and a quad core CPU as well. Reply
  • tipoo - Wednesday, March 28, 2012 - link

    Huh, the Vita actually has 128mb dedicated video memory, can't find the bandwidth though. Reply
  • pickica - Monday, April 02, 2012 - link

    We should also consider a possible higher clock on Vita. Reply

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