Technical Comparisons

As has quickly become tradition for us, to close out our look at the Midgard architecture we want to spend a bit of time comparing it to other SoC GPU architectures. As this is not a performance or benchmark article we aren’t going to dwell on the subject too much, but we find it’s helpful to get a high level overview of theoretical performance.

To do this we’ll take a quick look at theoretical performance for FP32 FLOPS, along with pixel and texel throughput. As this is a purely theoretical comparison it doesn’t (and can’t) take into account architectural efficiency, nor can it take into account real-world clockspeeds. But none the less it gives us something of a baseline.

To that end we asked ARM what a reasonable high-end Mali-T760 configuration might look like. T760 can scale up to 16 shader cores, but as we’ve seen in these scalable designs it’s very rare for anyone to build a SoC that actually takes the number of cores up to the architecture’s limit. And since T760 was only released to customers back in October of 2013, there are only a handful of designs announced so far and none of them are particularly high-end. To that end ARM suggested that a Mali-T760 MP10 would be a reasonable approximation of a high-end shipping configuration, so that is what we’ve gone with.

GPU Specification Comparison
  NVIDIA K1 Imagination PVR GX6650 ARM Mali-T760 MP10 AMD A4-1350
FP32 ALUs 192 192 100 128
FP32 FLOPs 384 384 200 (340) 256
Pixels/Clock (ROPs) 4 12 10 4
Texels/Clock 8 12 10 8
GFLOPS @ 300MHz 115.2 GFLOPS 115.2 GFLOPS 60 (102) GFLOPS 76.8 GFLOPS
Architecture Kepler Rogue (6XT) Midgard (T700) GCN 1.1

Briefly, we can see that as far as theoretical shading performance is concerned, our theoretical Mali-T760 would push 60 GFLOPS when counting MADs (20 FLOPS/clock/core). Or when using ARM’s preferred metric of MAD plus a dot product (34 FLOPS/clock/core) this becomes 102 GLOPS. How you count ends up being important here as it means the theoretical throughput of the T760MP10 is either close to something like AMD’s A4-1350, or close to the very high end configurations that NVIDIA and Imagination will be peddling.

On the other hand T760MP10’s pixel and texel throughput looks very good, easily exceeding both our AMD and NVIDIA configurations on both and specifically more than doubling the pixel throughput. Pixel throughput is going to be especially important going forward as these SoCs get paired with increasingly high resolution displays – the TV industry has in recent years become big SoC consumers and 4K TVs are growing in popularity – so being able to push a lot of pixels will in turn be helpful for pushing such displays. However ARM’s efficiency technology such as Transaction Elimination and AFBC will also have to play a big part here, as writing that many pixels per clock raw would consume a large amount of memory bandwidth, something SoCs rarely have to spare.

Final Words

With apologies in advance to ARM, wrapping up this article the first thing that comes to mind is something we wrote when looking at Imagination’s Rogue architecture earlier this year: “So it’s with some hope and a bit of luck that this might get the ball rolling with the other SoC GPU vendors, getting them to open up their doors a bit more so that we can see what’s inside their designs.”

It’s safe to say then that we have indeed been lucky about getting other SoC GPU vendors to open up about their architectures. ARM’s decision to come take a seat at the “open architecture” table has given us a great opportunity to see into the heart of another SoC GPU and to better understand and appreciate just what’s going on under the hood when we look at Mali powered products. Plus in opening up on their GPU architecture, we have been given the chance to see what just may be the least conventional GPU of the modern era.

When ARM first began to brief me on the Midgard architecture, they told me that it would be something unlike anything else we’ve seen before, and while I believed them I don’t believe that description is quite strong enough to get across just how surprised I was by ARM’s autonomous, TLP insensitive shader design. It took the better part of a few days even after the briefing to really internalize just what they had done, and while it seems simple (and very cool) in retrospect, going for an unorthodox architecture certainly throws you for a loop at first after spending several years covering the world of wavefront-driven architectures.

As for Midgard and its resulting products, this stands to be an interesting and exciting time for ARM. The finalization of OpenGL ES 3.1 and the announcement of the Android Extension Pack means that some of the functionality that ARM has had to sit on thus far is finally going to be exposed and used. And meanwhile with 64bit Android coming up and ARM’s 64bit Cortex-A5x processors similarly near, ARM can begin exploiting some of that shared 64bit development that ARMv8 and Midgard went through.

At the same time however ARM also will face the same struggle for market share that the other SoC GPU vendors also face. As we’ve discussed in the past, the SoC GPU market is full of competitors, some who make their own SoCs and hence won’t be ARM GPU customers, and others who are in the licensing business just as much as ARM. With the latest generation Mali-T700 series parts ARM already has some T760 wins with MediaTek, who will be using T760 with their mid-range Cortex-A53 SoCs. But at the same time I’d love to see what flagship-caliber device would look like with a T760, so hopefully we’ll get that chance over the next year.

This incidentally is all the more reason to be open right now, as it’s that much easier to convince your immediate customers and even build a brand among end users when they can freely learn more about your products and how they operate. To that end the “open architecture” table remains open, and as we shift to the next generation of SoCs and next wave of SoC GPUs, with any luck this won’t be the last time we get to learn more about the GPUs that are increasingly in our everyday devices.

Tricks of the Trade: Transaction Elimination and Frame Buffer Compression
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  • darkich - Friday, July 4, 2014 - link

    You guys are missing the fact that Snapdragon 805 can reach a much higher memory bandwidth than Tegra K1. Reply
  • TheJian - Saturday, July 5, 2014 - link

    But it still loses to K1 in most gpu stuff (all?). You're forgetting AMD/NV have had 20yrs of trying to figure out how to get the most they can from bandwidth for gaming. The devs have had that long working with their hardware also (game devs I mean). Everyone else has to play catch up here for years as they've never had to do anything game wise until last year or so as android etc gaming pumped up a bit.

    That is why you see ZERO Qcom optimized games (or did I miss one?) :) It's easier to optimize for a chip you already know inside out (amd/nv). I even went to Qcom's gaming page just to see if there were any games they had on their list that were REQUIRING snapdragon to see xx effects etc. There were none last I checked. All the games are just on googleplay with no snapdragon mention (like on NV games they say THD, and these games look quite a bit better than the regular versions) as they appear to work on ALL players chips. Google seems to be realizing K1 is where you want to be on gpu's at least for gaming centric stuff/automotive and I'd expect devs to continue to favor NV for optimizations as they don't need to learn a thing about k1 it's KEPLER which they've already spent 2yrs+ playing with (probably longer as they get dev versions long before we get a retail card so games can be made/optimized for them by the time they hit).

    At 20nm xbox360/ps3 will be left behind as new games keep getting made on mobile. If you're not on xbox1/ps4 you'll be buying some cheap 20nm console box that has cheap games ($2-20 vs. $60 for xbox1/ps4) and as good or better graphics than last gen xbox360/ps3. GDC 2013 & 2014 surveys show devs are already massively making games for mobile and as 20nm kicks in everyone has K1 power levels or more. These android consoles/tv's etc will have more tricks than those ancient consoles so you should be able to get much better gaming experience on them for $100-200. The games pricing alone is a draw for poor people. With the ports happening right an left now of quality PC/console games and super cheap pricing there is even more reason to run to mobile for poor people who never played them before (half-life2, trine2, Serious Sam3BFE, none sold more than 11mil or so). There are a billion android users and most clearly have played none of this stuff even the console ports like Final Fantasy games, GTA games etc (on or off PC also doesn't matter) haven't been played by more than 10mil or so combined each. Lost of great stuff for poor people to pick up for under $10 in ports until the REAL new games for mobile hit this xmas/next xmas. All of the stuff the dev surveys show they've been working on will hit this year or next, and they are not angry birds games.
    Reply
  • przemo_li - Tuesday, July 8, 2014 - link

    Alternative view on Google stance:

    Nvidia is just first vendor that allowed them to show more features than are possible on Apples A7.

    (Mobile-only vendors are not interested in full OpenGL...)
    Reply
  • TheJian - Sunday, July 6, 2014 - link

    If they're worried about lawsuits (odd they'd say that without merit), they must have had their lawyers tell them they'd be sued due to stealing tech that is probably from AMD/NV. DMCA takedowns, completely closing the kimono so to speak shows they are afraid for good reason. It isn't just competitor crap as nobody else is afraid of that it seems. The same tricks are being used by almost everyone to a large degree. So it seems to me they clearly owe someone some money and don't want to pay. They will probably show their details once they remove that stuff from a future gen soc or never I guess if they just can't remove it for some reason :) Reply
  • mczak - Thursday, July 3, 2014 - link

    You could add Intel HD graphics (baytrail) though. Also quite interesting architecture-wise imho.
    btw some small correction wavefront size for amd (gcn) is 64, not 16 (I think this was wrong on older anandtech articles too). The simd size is 16 indeed but the same instruction is executed for 4 clocks always (on 16 different elements of the wavefront each clock).
    Reply
  • mczak - Thursday, July 3, 2014 - link

    Here's actually an explanation how the wavefront size of 64 works for gcn:
    http://devgurus.amd.com/thread/168154
    Reply
  • Achtung_BG - Thursday, July 3, 2014 - link

    My first touch phone is black LG Viewty in 2008 with Mali GPU :) :) :) If you have new article for android extention pack comparison with full Open GL will be very intrasting. Reply
  • Jedibeeftrix - Thursday, July 3, 2014 - link

    yes please.

    i'd like to know:
    1. how long until the AEP is rolled back into what will be OpenGL ES 4.0
    1.1. whether it represents a subset of an existing OpenGL full-fat version (eg 4.4)
    2. how this compares to DX 11.2 feature wise
    2.1. whether AEP will be expanded in OpenGL ES 4.0 to make it broadly DX 11.2 compliant
    Reply
  • przemo_li - Tuesday, July 8, 2014 - link

    1) Never. (Though, separate extensions, can get into ES. AEP is just thin bundle over many other extensions)
    1.1) Yes. OpenGL 4.x is still capable of running AEP code.
    2) DX11.2 is single vendor en-devour currently... (And You really should compare to F(eature)L(evel)11_2).
    2.1) WHY?

    Why on earth You need all those things?

    Industry move in different direction. (Mantle, DX12, Metal, AZDO)

    Doing stuff efficiently is new mantra now.

    Adding more stuff from DX FL11_2 (Yes if You talk about features You MUST use F(eature)L(evels)!!!), would only complicate things for OpenGL ES.

    We need AZDO.
    Reply
  • Kevin G - Thursday, July 3, 2014 - link

    I can see Qualcomm's concerns about a shader arms race in mobile: it has already happened on the CPU side without much benefit to the consumer. However, with the explosion in screen resolution in tablets, a spec race here would have a more tangible benefit for consumers. It sitll boggles my mind that a retina iPad has 50% more pixels and a slower GPU than my desktop system with a 1080p monitor driven by a GTX 770. My sole concern would be temperatures and power consumption.

    Well if Qualcomm isn't going to disclose the information, how much can be implied from driver information? Qualcomm purchased the mobile Radeon drivision from AMD back in 2009 and then came up with the anagram Adreno. If they're still using a design based upon what they got form AMD, it'd be reflective in similar drivers. If they've come up with a new architecture, it too would be evident in radically different drivers. The details would be lacking of course but some generalities could be made.
    Reply

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