The iPhone Becomes a Gaming Platform: Enter the PowerVR SGX

Now that we’re familiar with the 3GS’ CPU, it’s time to talk about the GPU: the PowerVR SGX.

Those familiar with graphics evolution in the PC space may remember Imagination Technologies and its PowerVR brand by their most popular desktop graphics card: STMicro’s Kyro and Kyro II. The Kyro series used the PowerVR3 chips and while STMicro ultimately failed to cement itself as a NVIDIA competitor in the desktop, the PowerVR technology lived on in ultra-mobile devices.

The SGX is on Imagination Technologies’ fifth generation of its PowerVR architecture, and just like the Kyro cards we loved, the SGX uses a tile based renderer. The idea behind a tile or deferred renderer is to render only what the camera sees, not wasting clocks and memory bandwidth on determining the color of pixels hidden by another object in the scene. Tile based renderers get their name from dividing the screen up into smaller blocks, or tiles, and working on each one independently. The smaller the tile, the easier it is to work on the tile on-chip without going to main memory. This approach is particularly important in the mobile space because there simply isn’t much available bandwidth or power. These chips consume milliwatts, efficiency is key.

The MBX-Lite used in the original iPhone was also a tile based architecture, the SGX is just better.

Also built on a 65nm process the PowerVR SGX is a fully programmable core, much like our desktop DX8/DX9 GPUs. While the MBX only supported OpenGL ES 1.0, you get 2.0 support from the SGX. The architecture also looks much more like a modern GPU:

Pixel, vertex and geometry instructions are executed by a programmable shader engine, which Imagination calls its Universal Scalable Shader Engine (USSE). The “coprocessor” hardware at the end of the pipeline is most likely fixed-function or scalar hardware that’s aids the engine.

The SGX ranges from the PowerVR SGX 520 which only has one USSE pipe to the high end SGX 543MP16 which has 64 USSE2 pipes (4 USSE2 pipes per core x 16 cores). The iPhone 3GS, I believe, uses the 520 - the lowest end of the new product offering.

A single USSE pipe can execute, in a single clock, a two-component vector operation or a 2 or 4-way SIMD operation for scalars. The USSE2 pipes are upgraded that handle single clock 3 or 4 component vector operations, have wider SIMD and can co-issue vector and scalar ops. The USSE2 pipes are definitely heavier and have some added benefits for OpenCL. For the 3GS, all we have to worry about is the single USSE configuration.

  iPhone 3G (PowerVR MBX-Lite) PowerVR SGX @ 100MHz PowerVR SGX @ 200MHz
Manufacturing Process 90nm 65nm 65nm
Clock Speed ~60MHz 100MHz 200MHz
Triangles/sec 1M 3.5M 7M
Pixels/sec 100M 125M 250M


In its lowest end configuration with only one USSE pipe running at 200MHz, the SGX can push through 7M triangles per second and render 250M pixels per second. That’s 7x the geometry throughput of the iPhone 3G and 2.5x the fill rate. Even if the SGX ran at half that speed, we’d still be at 3.5x the geometry performance of the iPhone 3G and a 25% increase in fill rate. Given the 65nm manufacturing process, I’d expect higher clock speeds than what was possible on the MBX-Lite. Also note that these fill rates take into account the efficiency of the SGX’s tile based rendering engine.

Enter the ARM Cortex A8 Final Words: Preparing for 3GS


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  • HelToupee - Wednesday, June 10, 2009 - link

    There's been one in the works for more than a year. ("> They've been stalling, though, and apple's releasing of new models every year is hurting, too. They originally were just aiming for jailbroken phones / ipods, but now want to enable full SDK support. I have cash set aside to buy one, if they'd just put them on sale... Reply
  • mesiah - Wednesday, June 10, 2009 - link

    Glad to see someone is working on this. From the video on the sight it looks like the latency on the controls is kind of an issue, and it looked like it wouldn't accept multiple button presses at the same time i.e. forward and right simultaneously. Could just be an issue with the way the interface with the iphone works, although the multiple button thing could just be me :P also, would like to see an analog stick. The days of on/off style movement controls are long gone. Reply
  • Lonyo - Wednesday, June 10, 2009 - link

    They've had the iPhone, and the iPhone 3G.
    They've sold quite a lot of them, using the same hardware.

    Now they are releasing a new product with faster hardware.

    Palm has the Pre, it has faster hardware.

    The problem here is that either Apple developers are going to have to develop for the (s)lowest common denominator (20million units), and either risk annoying customers by making them unable to use the stuff/forcing them to upgrade, or making applications which aren't sa impressive as they could be.
    The Pre has the advantage of being out later, so everything has the same base point (although it has no install base or history yet).

    While it's good Apple have improved their hardware, it will be interesting to see how the handle the software side (after all, they have been forcing programs to be forwards compatible with something which was unreleased at the time - OS3.0).

    Apple could be their own worst enemy with this faster hardware, and they have been seen to drop legacy support quite quickly already (Snow Leopard anyone?), things that other people can't get away with.
  • str1f3 - Wednesday, June 10, 2009 - link

    The problem with the Pre is that it's not meant for gaming. The SDK is only HTML and Javascript. There won't be any serious gaming on it. In the mobile phone area Apple is pretty much to themselves. Reply
  • Shadowself - Wednesday, June 10, 2009 - link

    Actually, I don't mind that Snow Leopard is going to be Intel only. With it coming out in September I would not suggest that anyone other than the bleeding edge crowd upgrade to Snow Leopard until October or November at the earliest. That makes the oldest Intel based Mac almost four years old.

    If I were still running G4s or G5s (PowerPC based) systems as of this coming November I clearly don't *need* the performance enhancements of a full 64-bit kernel and drivers, OpenCL or Grand Central Dispatch.

    While Leopard had nearly as shaky/buggy a start as Vista (though 99.9% of Mac users won't admit it), Leopard has reportedly morphed into a very stable and serviceable system. If you're keeping your Mac for 5+ years, sticking with Leopard might be a great option.
  • sc3252 - Wednesday, June 10, 2009 - link

    I think I read somewhere that developers for the Ipod would put in options to enable for the faster models. So you just check the box if you have a faster cpu and you get the cooler looking graphics. Reply
  • Pirks - Wednesday, June 10, 2009 - link

    The day WoW comes to iPhone is the day when I gonna buy the little bastard. I guess this will happen next year or so. I can almost hear Blizzard devs steaming away, downloading iPhone SDK and buyng more and more Macs. This thing is gonna freakin ROCK. Reply
  • sc3252 - Wednesday, June 10, 2009 - link

    Not now. The gpu and CPU are still way to slow to play anything like world of Warcraft, just look at some of the demos of the openpandora which uses the same CPU/GPU combo, it runs quake 3 around 22fps from what I can see and most of us now how much of a pushover that game is.
    I would expect that the next generation omap 4 might be able to run it being a dual core 1Ghz, but I would think it would still need a faster GPU. Also you have to imagine trying to play a game like world of warcraft with those controls, it would be terrible. You might see a game like eve do it since the game developers are very forward thinking, but not Activision blizzard.
  • Digitalhell - Wednesday, July 8, 2009 - link

    I've never seen Quake3 compiled for CortexA8 and OGL 2.0ES. The best Q3 currently available is actually designed for TI Omap 2/Samsung 6400 which are based on Arm11 processor core and Ogl 1.1 ES. Reply
  • monomer - Wednesday, June 10, 2009 - link

    While I don't see Blizzard releasing a mobile version of WoW anytime soon, just imagine the amount of time you could waste if they simply released an Auction House app. Reply

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