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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  • jasaero - Wednesday, June 10, 2009 - link

    Woops here's the link to the scorpion core info.

    http://www.insidedsp.com/Articles/tabid/64/article...">http://www.insidedsp.com/Articles/tabid...-Reveals...
    Reply
  • jasaero - Wednesday, June 10, 2009 - link

    More interesting info on Qualcomm's offering and smartphone SoC plan in general.

    http://brew.qualcomm.com/brew_bnry/pdf/brew_2007/T...">http://brew.qualcomm.com/brew_bnry/pdf/brew_2007/T...
    Reply
  • electricgrape - Wednesday, June 10, 2009 - link

    Any word on the lowly ipod touch? I've got Sero and I'll be damned if I'm going to leave $30/month just to pick up an iphone....so I use a touch :-) Reply
  • poohbear - Wednesday, June 10, 2009 - link

    i liked this review, especially the comparisons to 486 & older gpus, u know your crowd well.;) i actually prefer computer reviews but this was'nt abd at all. thanks again. Reply
  • tonjohn - Wednesday, June 10, 2009 - link

    As an iPhone 3G owner, do I stick with what I have or do I upgrade?

    Will the 3GS really be worth the extra money for current 3G owners to upgrade?
    Reply
  • rageguy34 - Wednesday, June 10, 2009 - link

    I wouldn't, I currentlt have an iPhone 3G and the new features even if 2x faster doesn't seem worth me spending $400 to upgrade. I'll just wait till next year when my contract expires and I will qualify for the new iPhone Reply
  • stuclark - Wednesday, June 10, 2009 - link

    ..all very interesting, but what about other smartphone platforms, such as Symbian's S60, which have handsets which far out-perform the likes of the iPhone and Pre?

    Take for example Samsung's i8910 handset, which runs S60 and is technically superior to pretty much anything else on the market. Here's it's spec sheet: http://innovator.samsungmobile.com/prd/sym/product...">http://innovator.samsungmobile.com/prd/...1%26plat....
    Reply
  • winterspan - Thursday, June 11, 2009 - link

    So tell me, what are these S60 handsets that "far out-perform" the iPhone 3GS and Pre?

    The Samsung i8910/Omnia HD uses the exact same TI OMAP3430 chip as the PRE. The OMAP3430 has the same 600Mhz Cortex-A8 and PowerVR SGX as the iPhone, although the iPhone may be SGX520 where the OMAP3430 uses the SGX530.

    Quit spreading BS!
    Reply
  • rageguy34 - Wednesday, June 10, 2009 - link

    Anand,
    Why doesn't apple use the tegra instead of the ARM processor, does tegra use up too much power?
    Reply
  • psychobriggsy - Wednesday, June 10, 2009 - link

    Tegra is ARM11, so it won't be as fast. No idea how the GPUs compare though. If Apple are designing an in-house product that uses A8 or A9 with NEON, they probably wanted to use the A8 earlier.

    Also there is the matter of support for Apple to use it, having to learn a new SoC (who knows - this SoC could be pin compatible with the old one) and so on. Otherwise they could have used the TI OMAP that the Pre uses...
    Reply

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