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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  • araczynski - Monday, June 15, 2009 - link

    blah blah blah same crappy gameboy resolution screen blah blah blah talk to nokia blah blah blah.

    maybe if half the price of the stupid thing went into the device instead of paying for all the worthless marketing they'd have a killer device that i would gladly pay $130 a month for for unlimited data service.

    ah well, maybe in a few years.
  • punkball - Saturday, June 13, 2009 - link

    I dunno why ,i have a good feeling
    not knowing much at all about (only what seems to be a negative
    evaluation on parts; by the community).
    This phone its main uphearst performace being, we'll see a comprised Flash/Flex player on the iTunes store ?a good deal onwards agreed on a Mac-device friendly version of the Flash Player?? Anyone else hoping/caring?
  • lateef - Friday, June 12, 2009 - link

    does anyone know if the radio/wireless chipset been upgraded in the 3gs rather than a tweak
  • iwodo - Friday, June 12, 2009 - link

    Arh, interesting question. I think everyone were too concentrated on its CPU, Memory and GPU and forgot the most fundamental / important issues.
    To be honest iPhone is rather weak for its Radio Reception. I think this is partly due to Infineon are new to Mobile Chipset.
    Is there an updated chipset to fix iPhone Comparatively poor quality reception?
    ( Last time i heard the 7.2Mbps speed increase has to do with Firmware unlocking, so i am not sure if the chipset has been updated )
  • PhilipOrr - Friday, June 12, 2009 - link

    Was talking with the Apple engineers at WWDC which technical data sheets to look up concerning the GPU within the new iPhone. It's the PowerVR SGX 535.

    This chip is one up from the Palm Pre which is the PowerVR SGX 530.

    The difference between these is more video based than anything else. 535 has hardware acceleration for H.264 encode/decode, MPEG 4 and JPEG. It also handles HD content to 720p in real time.

    These specs seem to give a hint to what Apple are planning for future upgrades of the iPhone or other device. Suggesting, that if your developing for the 3GS then you're already developing for the next generation too.
  • jasaero - Friday, June 12, 2009 - link

    My guess is that the 535 was used more for optimizing the video option on the phone than for any future planned uses. Not required to do video, but is extremely useful in reducing file sizes of video output and may help with some of the video editing functionality it supossedly has. So far Apple hasn't really preplanned any added functionality so much as reacted to demand for certain features they seemed to have left out useablity and performance trade off. Copy, cut, paste being the most glaring example. Basically I am quite doubtful they have a handset like the Omnia HD that probably uses this same chip in their sights just yet.
  • iwodo - Thursday, June 11, 2009 - link

    I really hope anand do some detail article on Mobile Tech. MIPS, ARM, difference between ARMv6 and v7. SnapDragon and OMAP. I mean if iPhone uses a SOC that is 90% the same as TI's OMAP, why not just buy it from OMAP? Do different implementation of ARM matters? How does Tegra compare to SGX, what about Mani ( ARM ) 's graphics department?

    There are about 10 dozens more questions i hope anand could answer. The truth is, as a tech news reader, i haven't been as excited as this for a long time. PC are already way too powerful then 90%+ of our needs. That is why Netbook are so popular. They are cheap, and gets the job done.

    The next battle, and most interesting development in the next decade will be on Mobile front. Where ARM and PowerVR dominate. PC tech are used to Intel and ATI/Nvidia so ARM and PowerVR's tech are Alien to us.

    I really hope there will be more in depth article about Mobile Technology. The only thing that interest me in PC is development of SSD.
  • Anand Lal Shimpi - Friday, June 12, 2009 - link

    I've been dabbling in it for a while but I think I agree with you. Such a comparison may be necessary. I'm going to start chasing some of these technologies and see where I end up. If I find something sufficiently interesting, I'll be sure to share :)

    Take care,
  • iwodo - Friday, June 12, 2009 - link

    Thanks. Hoping for more ARM info soon.

  • AnnonymousCoward - Friday, June 12, 2009 - link

    I agree. Apple should be buying OMAP instead of the ASIC. I think digital camera companies will be going that route too.

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