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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  • sxr7171 - Wednesday, June 10, 2009 - link

    A Dreamcast in the palm of your hand. Please port some Dreamcast titles to this phone. I would order mine this minute. Reply
  • squngy - Wednesday, June 10, 2009 - link

    So how would these systems compare with the PSP or DS?

    If we're talking about games, then it would make sense to know where it stands compered to other popular gaming devices.
    Reply
  • Anand Lal Shimpi - Wednesday, June 10, 2009 - link

    Compared to the DS, the iPhone 3G (and 3GS) are both way more powerful. That thing uses an ARM9E based processor and runs at no more than 133MHz I believe. The Cortex A8 should run circles around it. According to Wikipedia, the DS' "GPU" can reach a peak of 120K triangles per second...the first iPhone is capable of 1M per second. The iPhone is a superior hardware platform from a specs standpoint.

    The PSP is a bit more difficult of a comparison. It's got two MIPS cores plus a GPU. I haven't looked deeply into its architecture but I believe the 3GS should still be faster.

    Memory size is a huge limiting factor. The PSP has 2MB of video memory, 32MB of application memory and 4MB of embedded DRAM? The DS is even worse, it only has 4MB of RAM and < 1MB of video memory!

    The original iPhone had, what, 128MB? Everyone is expecting 256MB from the next-generation model.

    It's only a matter of time before handheld consoles are replaced by something like the iPhone. Console makers have to subsidize the cost of their hardware across games, cellular providers already subsidize the hardware costs of smartphones. There's huge potential here.

    Take care,
    Anand
    Reply
  • Anand Lal Shimpi - Thursday, June 11, 2009 - link

    Update - digging more into the PSP specs it's quite possible that the PSP is a faster gaming platform. It's difficult comparing CPUs since we're talking about a cross-architecture comparison, but on the GPU side the PSP appears to have more raw power. How that translates into real world performance compared to the PowerVR SGX in the 3GS remains to be seen. The 3GS most definitely has an efficient core.

    The memory comparison is still valid, especially with the 3GS at 256MB of RAM things get even more interesting.

    Take care,
    Anand
    Reply
  • Jovec - Wednesday, June 10, 2009 - link

    Wireless companies don't subsidize anything - they simply have an absolutely huge markup that then can then discount you $50 or $100 with a contract. Reply
  • ViRGE - Wednesday, June 10, 2009 - link

    Depending on whether we're talking about the DS or the DSi, the main CPU is 66mhz or 133mhz respectively (always operating at 66mhz in DS mode). Both come with the ARM7 co-processor, which runs at 33mhz. The RAM value for the DS is right, meanwhile the DSi has 16MB. RAM's a bit iffy of course, the DS isn't running an operating system in the background and Slot-1 affords some in-place use of assets (albeit not true in-place execution like the GBA that let it get away with virtually no RAM). At any rate, the DS is still less powerful than the iPhone 3GS obviously.

    You're correct about the PSP, it has 2 MIPS processors (one for CPU use, one as a graphics processor) that can run between 22mhz and 333mhz. Most games for it are at 222mhz, a small number of titles push it to 333mhz. In raw CPU performance the 3GS is likely ahead, in GPU performance however it's entirely possible the PSP is still in the lead. When properly optimized the PSP is capable of near-PS2 graphics, which looking at the SGX's specs may be just a bit more than it can do. But we'll have to see what's done with it.

    The more limiting factor however is power consumption. The DS Lite is a champ here - on the lower screen brightness settings it gets over 10 hours running at full tilt. That's Nintendo's tradeoff on performance and power. The PSP isn't nearly as good, but even when everything is cranked up it can do about 4-5 hours (I'm going to ignore the UMD here), more if it's a 222mhz game.

    Both of these are well in excess of what the iPhone 3G got on its most demanding games. Even though the 3GS is faster, games aren't going to offer it much of an opportunity to drop to a lower power state since they're tasks that never end. For a 3G game I'd expect better battery life (50%, so 3 hours maybe?), but for a 3GS game it's likely going to be even worse.

    As you note the 3GS can eat more power, so if devs try to max it out (and they will, there's 20 years of console history that says shiny sells) it's reasonable to expect that it'll crash harder than even the 3G. Unless the SBX eats significantly less power, the worst case battery life scenario for the 3GS is going to be far worse than any dedicated handheld on the market, and worse than the existing 3G and iPod Touch.

    To that end, unless Apple can reign in on developers and make them NOT max out the hardware, I don't see handhelds going away any time soon. You'll get some convergence (e.g. solitaire) but the battery/hardware balance for a phone and a handheld are completely different. A gaming platform that only gets a couple of hours is a Sega Game Gear (or a Nomad, for the sadistic), and at least that had removable batteries.
    Reply
  • psychobriggsy - Wednesday, June 10, 2009 - link

    Confirmation of 600MHz and 256MB RAM: http://www.t-mobile.nl/iphone/specificaties.html?W...">http://www.t-mobile.nl/iphone/specificaties.html?W... Reply
  • sxr7171 - Wednesday, June 10, 2009 - link

    I GS must be faster than the N95's 3D acceleration as well, I know the 3G was slower, but this looks much faster. I've seen 3D demos on the N95 and wow they were impressive. At that 320x240 resolution it probably performed better than the PSP. Reply
  • fyleow - Wednesday, June 10, 2009 - link

    The greatest weakness of the iPhone is the controls. Developers can get pretty innovative with the touch screen and accelerometer but really they can only do so much. id did a great job with Wolfenstein on the iPhone but the controls are still not as precise as physical buttons, and the controls take up the already limited screen estate of the phone.

    Nintendo threw as many input methods as possible with the mic, touch screen, physical buttons, and now camera. They also put in dual screens. The result is that developers could get wildly creative and I think it has been key to the DS' success because it allowed for some pretty innovative games.

    I've yet to see many "serious" games for the iPhone; most appear to be catered to very casual gaming. There's a huge market for that as evidenced by the Wii, but it's not ready to displace the dedicated hand held consoles yet.

    Yeah we'll probably see convergence happen down the road, but not in this or the next generation.

    Reply
  • mesiah - Wednesday, June 10, 2009 - link

    The average phone user doesn't care much about games and game controls, so I don't really see apple or palm incorporating these into their phones and cluttering up the interface. But all it would take is for a company to create a peripheral that, say, the iphone snaps into and docks with that has an analog stick, some buttons, and some hand grips. Could even make it so it folds up when not in use. Something like that could really open up possibilities for gaming on iphone or pre. Just thinking about it makes me a little giddy hehe. Nintendo hand helds have always been too cheesy for me, but I can't bring myself to spend big money on a psp. Now if I can justify it with "but, its a phone and so much more." maybe my conscience would say "hey, your right! Go ahead and buy it." Reply

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