The Mali-400

Now that we've settled the issue of what type of GPU it is, let's talk about the physical makeup of the Mali-400. The Mali-400 isn't a unified shader architecture, it has discrete execution hardware for vertex and fragment (pixel) processing. ARM calls the Mali-400 a multicore GPU with configurations available with 1 - 4 cores. When ARM refers to a core however it's talking about a fragment (pixel shader) processor, not an entire GPU core. This is somewhat similar to NVIDIA's approach with Tegra 2, although NVIDIA counts each vertex and fragment processor as an individual core.

In its simplest configuration the Mali-400 features a single combined geometry front end and vertex processor and a single fragment processor. The 400 is also available in 2 and 4 core versions, both of which still have only a single vertex processor. The two core version has two fragment processors and the four core version has four fragment processors. Note that ARM decided to scale fragment shading performance with core count while keeping vertex performance static. This is likely the best decision given current workloads, but a risky one. NVIDIA on the other hand standardized on a 1:1 ratio between fragment and vertex processors compared to ARM's 4:1 on a 4-core Mali-400. The 4-core Mali-400 MP4 is what Samsung uses in the Exynos 4210.

ARM, like Qualcomm, isn't particularly interested in having the details of its GPUs available publicly. Unfortunately this means that we know very little about the makeup of each of these vertex and fragment processors. I suspect that both companies will eventually learn to share (just as AMD and NVIDIA did) but as this industry is still in its infancy, it will take some time.

Earlier documentation on Mali revealed that the GPU is a VLIW architecture, meaning each processor is actually a collection of multiple parallel execution units capable of working on vector data. There's no public documentation indicating how wide each processor is unfortunately, but we can make some educated guesses.

We know from history that AMD felt a 5-wide VLIW architecture made sense for DX9 class games, later moving down to a 4-wide architecture for DX11 games. AMD didn't have the die constraints that ARM and other SoC GPU suppliers do so a 5-wide unit is likely out of the question, especially considering that Imagination settled on a VLIW4 architecture. Furthermore pixels have four color elements (RGBA), making a VLIW4 an ideal choice.

Based on this as well as some internal information we can assume that a single Mali fragment shader is a 4-wide VLIW processor. The vertex shader is a big unknown as well, but knowing that vertex processing happens on two coordinate elements (U & V) Mali's vertex shader is likely a 2-wide unit.

Thus far every architecture we've looked at has been able to process one FP16 MAD (multiply+add) per execution unit per clock. If we make another assumption about the Mali-400 and say it can do the same, we get the following table:

Mobile SoC GPU Comparison
  PowerVR SGX 535 PowerVR SGX 540 PowerVR SGX 543 PowerVR SGX 543MP2 Mali-400 MP4 GeForce ULP Kal-El GeForce
SIMD Name USSE USSE USSE2 USSE2 Core Core Core
# of SIMDs 2 4 4 8 4 + 1 8 12
MADs per SIMD 2 2 4 4 4 / 2 1 ?
Total MADs 4 8 16 32 18 8 ?
GFLOPS @ 200MHz 1.6 GFLOPS 3.2 GFLOPS 6.4 GFLOPS 12.8 GFLOPS 7.2 GFLOPS 3.2 GFLOPS ?
GFLOPS @ 300MHz 2.4 GFLOPS 4.8 GFLOPS 9.6 GFLOPS 19.2 GFLOPS 10.8 GFLOPS 4.8 GFLOPS ?

Based on this estimated data alone, it would appear that a four-core Mali-400 has the shader compute power of a PowerVR SGX 543. In other words, half the compute horsepower of the iPad 2's GPU or over twice the compute of any smartphone GPU today. The Mali-400 is targeted at 275MHz operation, so its figures are likely even higher than the competition. Although MADs are quite common in shader execution, they aren't the end all be all - we need to look at application performance to really see how it stacks up.

Understanding Rendering Techniques GPU Performance: Staggering
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  • ph00ny - Sunday, September 11, 2011 - link

    Btw you can launch search by holding down the menu button Reply
  • Aloonatic - Sunday, September 11, 2011 - link

    Just curious, but have MS given up on the smartphone market? Or have I just missed out on all the new (or soon to be release) WP7 devices?

    At this rate, I'm just going to have to go with Android and a SGS II, even though I'd love a WP7 phone, but what there is out there are just all old handsets, and I'd have to change carrier to get one now too, as T-Mobile (UK) don't seem to sell them at all any more!?!?!?111!
    Reply
  • dagamer34 - Sunday, September 11, 2011 - link

    If I had to guess, OEMs are working on their new handsets, but want to load them with Windows Phone 7.5, which only RTMed officially a few weeks ago.

    My best guess is we'll see some more phones around October or so, with a Galaxy S II shaped WP7 device.
    Reply
  • Aloonatic - Sunday, September 11, 2011 - link

    Well, October is what I figured too, but... We're already over a week into September and there still aren't any "coming soon" 7.5 devices to be seen anywhere, so I'd be surprised if October (as in the start of October) is anything but wishful thinking.

    It starting to seem like MS just aren't that bothered. Where's the "ooh, look at this coming soon phone" stuff? The SGS 2 like WP7 phone has been mentioned all over the web for months, but there's nothing remotely official, and with only the odd photo shopped image from net dreamers.

    It's a shame, as I'm not a fan of Apple, their products or how they behave. And I've tried Android and been annoyed by their poor updating system, where too many companies have been allowed to let year old hardware languish at the back of the update queue (if it's lucky) while the new devices get all the attention and you're left with juddering menus and in some cases shocking security holes.

    Maybe it's just me, and my problem, for hoping that WP7 might offer a solution to my woes, but MS are just leaving this all waaaaaaayyyyy too late. By the time they get to the party someone will be handing them a bin bag and asking them to help clear up.
    Reply
  • ph00ny - Sunday, September 11, 2011 - link

    What do you mean? It was in the video presentation for the mango announcement month or two ago

    http://www.youtube.com/watch?v=ABO_LyD_SXs

    right around :40 he whips it out of the pocket. I guess he couldn't wait to use it as his daily phone
    Reply
  • Aloonatic - Sunday, September 11, 2011 - link

    Oh, so they have a few units the they showed on a video presentation that who saw exactly?

    Yes, I may have been exaggerating slightly before (and I know that that doesn't stand on geek boards) and we've all (well, a reasonable percentage, as I am sure that at least 1 person reading this hasn't) seen the "leaked" video that no one *wink wink* should video and get out.... But really, there's nothing to be seen here. Those videos are no more proof of a finished product than a concept car at a motor show.

    I'm just disappointed that they hare dragging their feet on this product, and really don't seem to care either.
    Reply
  • ph00ny - Sunday, September 11, 2011 - link

    This was posted on a lot of major tech blog/news sites. As for devices, there are quite a few announced devices but they're all waiting for the mango update Reply
  • vision33r - Monday, September 12, 2011 - link

    Samsung phones are outdated in one quarter. They release small updated features to the same platform.

    The Galaxy line had 4-5 different variant versions within the same year.

    This makes update very difficult for them and also buyer confusion.

    I'll stick with HTC, since Samsung takes forever to fix software and issue timely updates.
    Reply
  • ph00ny - Monday, September 12, 2011 - link

    which device outside of the US carrier branded ones didn't get updates as soon as HTC devices? In fact, which android device manufacturer doesn't release 4-5 different variants within the same year? Reply
  • aegisofrime - Sunday, September 11, 2011 - link

    Had mine here in Singapore for about 3 months now, and you Americans will be joining the party with plenty of custom ROMs and kernels to choose from :)

    So yeah, welcome to the party!

    This forum will probably be your new best friend now:

    http://forum.xda-developers.com/forumdisplay.php?f...
    (Galaxy S II Original Android Development)
    Reply

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