The GPU and its Performance

We’ve gone through, in great depth, the CPU in the new iPhone 3GS. But the GPU is arguably the more interesting upgrade. I’ve already covered the GPU pretty well so I present you with a blatant copy/paste of what I’d already written:

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. Update: Thanks to BlazingDragon and psonice for pointing out that the 3GS may in fact use a PowerVR SGX 535 based on drivers on the iPhone 3GS. It could still use a lower end SGX core and use the 535's driver, but there's at least the possibility that the 535 is under the hood of the 3GS.

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.

Obviously all games on the app store were designed for the PowerVR MBX-Lite and the SoC in the iPhone/iPhone 3G/iPod Touch. Some do run faster/smoother on the 3GS thanks to the faster CPU and GPU, but the new hardware should enable an entirely new class of game in the future.

Developers will have to deal with a segmented user base, since there are around 20 million PowerVR MBX-Lite based phones and a bit over 1 million SGX based 3GSes in the market.

The GPU Comparison

There are obvious limitations to the iPhone 3GS being used as a gaming platform. But there are also obvious limitations to the 3GS being used as a camera or a video player. The point isn’t that the 3GS could replace the Nintendo DS or the Sony PSP, it’s that the iPhone could get you maybe 80 - 90% of the way there.

There are serious control and battery life limitations, but the platform has the right combination of hardware, a software delivery system and ubiquity to at least be considered a viable gaming system. It has a much more powerful CPU/GPU combination than a Nintendo DS, now what it needs is the iPhone equivalent of Mario. Perhaps Apple should buy a game developer.

The obvious smartphone GPU comparison here is the Palm Pre. The TI OMAP 3430 used in the Pre (good job Palm on full disclosure there, just add clock speeds and you’ll get an A+) is a very similar SoC to the Samsung chip in the iPhone 3GS. As such, it also has a PowerVR SGX core.

The CPU and its Performance Camera and Video Capture
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  • shank2001 - Wednesday, July 8, 2009 - link

    Wow, talk about fanboyism. Let me get this straight, just because it is an article on the iPhone you feel there is no knowledge to be gleaned from an in depth article like this one? You would rather that no one wasted YOUR time with more articles about the iPhone, is that right?

    Well I, for one, learned a lot about smartphones in general, and not just the iPhone, but I especially loved this article getting into the nitty gritty of the iPhone.

    The iPhone happens to be the best smartphone out right now... it might not be that way forever.... probably not. But I really like the direction Apple has been taking the smartphone market since they introduced the iPhone.

    After years of using so called "smartphones" running windows mobile, and Pocket PC OS, etc. the iPhone is a breath of fresh air, and is the best smartphone I have ever owned.

    It took Apple to force the market into making a true smartphone. I am glad that Palm has woken up from their stupor and come out with the Pre, I hope it is enough to turn around their fortunes.

    Although, for me, it does not come close to the iPhone, but then again, most of the things that people seem to dislike, I actually LOVE... like the touchscreen typing for example. I am way faster typing on my iPhone than I ever was on my old smartphones with the chicklet keyboards. You just have to trust the autocorrection... once you learn to trust it, it is amazingly speedy. I no longer think twice about typing lengthy comments, such as this one, on my mobile phone any more! I just do it.

    I have not yet heard a single viable reason to hate the iPhone, I think I will coin the term "Hateboy" to describe these boys, they certainly act like little kids filled with illogical hate. No matter if you love the iPhone or hate it though, you have to admit that the iPhone DID revolutionize how smartphones will work from now on. Kudos to Palm for recognizing this fact, hopefully others will as well. The consumer is who wins. And good for Apple for finally getting some recognition for their amazing products that have led the industry from the very beginning in so many ways.
    Reply
  • Myrandex - Wednesday, July 8, 2009 - link

    I will agree that the iPhone revolutionized the smartphone market, and it has done some pretty amazing things pretty darn well good, but I still have some key complaints that prevent me from EVER getting one, unless I see a fundamental change in Apple, which never happens.

    I will not buy a phone without a Standard connection interface. Just beause the iPhone is so popular doesn't mean that its proprietary apple dock connector is standard. Use standard mini USB or micro USB, or I won't touch it.

    The touchscreen keyboard is good, and it does have a nice autocorrection, however I still prefer tactile feedback. As good as that keyboard is, there is no way that I can type without looking at the keyboard like I can on my current HTC smartphone. The keyboard on my phone is very comfortable, and I'd imagine that I am faster on that than some people on their computer keyboards. I've written 4 page emails from my phone with minimal effort. Some words I do not want autocorrected either. Acronyms many times are autocorrected by a phone, or names too, but many times I type these accurate and want them to stay that way, which on a software keyboard it slows you down because of verifying every key. Passwords also are like this, much slower when I'm using an iPhone compared to my smartphone (my fiancee has had both the 1st Gen iPhone and the iPhone 3G).

    iTunes. I hate it. If I have to use it to use a phone, I will not use the phone. I want USB Mass Storage device access, I want to copy and paste music to my phone with my organization that I have already decided upon (whether or not tags are filled out correctly), and I don't want to have to sync it, just copy and paste what I want ONTO it and OFF OF it. I want to be able to copy music from my desktop onto my phone, plug my phone into my laptop, and copy it off of there. No profiles, no syncing, just pure file access. Thanks Microsoft, no thanks Apple.

    Apple controlling application. This is corrected with jailbreaking, however I choose to vote with my wallet. I do not want to support a company that enforces this. Any application that I find that I want written for my phone, I will install on my phone. If it offends someone at Apple, then more power to me to want to install it on my phone. They will not make a dollar off of me for their stongarmed tactics.

    There are probably other small things as well, but those are the major ones.

    Jaosn
    Reply
  • christinme7890 - Thursday, July 9, 2009 - link

    if you are using your keyboard without looking you are most likely driving...a large portion of the accidents in cars happen because idiots are using their phones while driving. If you are doing this please stop or you could kill someone...no joke. I had a friend whose mom died because some idiot was text while driving.

    Second the itunes store is great for most people. Sure it doesn't have what you are looking for which is essentially a hdd but if it did then installing apps would suck. Why do you think the APP store is doing so well. Because it is a one stop shop. If I want a app, i go to the APP store and search for it and then click buy/install then sync and finished.

    If I were using a WinMo device I would have to first find a list of all the devs that offer the app i am looking for and visit each and every webpage and sit through all the trash that they claim their software does. Pay attention to the finding devs that produce the app I am looking for...this takes longer than you think, especially for a n00b consumer. I also have to pay attention to which WinMo OS the app supports. Many times you need the newest and greatest OS in order for it to work and when I had a PPC, verizon didn't let me have the latest upgrade to the OS. I had to hack the PPC to allow me to use the updated OS. Then once I find the right dev, the software is usually a lot more expensive because there is no immediate competition. So i end up paying a ton of money. Sure you can find free software that does similar but it is not backed by a good support system...merely a live forum. Then once I find the software I have to give them my credit card information and email address. I will more than likely end up getting a email daily from the company about their new crappy software. Now that I have spent 20 minutes entering in my underwear size and preferred deodorant brand I download my app. After downloading it I have to go through their custom install procedure. Then I have to hope that it installed correctly. Then if I want it to sync with my desktop I have to buy another piece of software and install it and then figure out how to get it to sync. So much hassle and running around and time wasted. I can install 1 APP store app in less than a minute and it could be a game that is 100mb installed over wifi.

    And about the music. Easy, you create what we call a playlist and drag and drop your music to the playlist and then sync your phone. You then play your playlist. Playlists are the same as folders. Not sure what is so difficult about that. Yes it would be nice to be able to connect my iphone to multiple computers to copy music but then you get what APPLE, along with every other business wants to avoid, and that is illegal sharing...duh. Just because people don't let you do anything you want doesn't mean you have to spew hate.

    "If it offends someone at Apple, then more power to me to want to install it on my phone." This attitude is selfish and you are probably one of those people that loves to steal and pirate software all the time. You care little for the developer and only about yourself.
    Reply
  • shank2001 - Wednesday, July 8, 2009 - link

    That was a good rebuttal comment. I agree with some of what you say, especially the having to look at the keyboard. It is a definite necessity. I do miss that about an actual physical keyboard.

    Reply
  • iwodo - Wednesday, July 8, 2009 - link

    This is no way fanaticism. But the general enthusiasm in terms of great technology improvement. It was an GREAT article from Anand. ( Yes i read it all, give me lollipops :D ) May be you are too young to figure this out.

    What drive you to see more SSD stuff? I want to see more SSD review too. Why? Simply because HDD it is the SINGLE bottleneck living inside out current Computer. Be it PC or Mac.
    Upgrading from an Core2Duo to Core2Quad or even Core i7, Double Channel to Tri Channel, DDR2 to DDR3, 2GB to 4GB Memory, Geforce 9500 to GTX 290.... If you are not a gamer, any of these upgrades, or even if you do ALL of these upgrades, wont even land you a 10% overall performance increase in your 90+% day to day usage of computer. And even if they do show more then 10% in benchmark. There is a very small chance these are even human / user perceivable.
    You will properly feel your system being faster if you reinstall Windows rather then upgrading your Hardware.
    That is why SSD is so important and many people want one. It actually brings Significant perceivable speed improvement that is not seen FOR MANY YEARS.

    The last time we seen any improvement was in the Pre Pentium 4 days...

    iPhone, or Internet Mobile Devices, are in exactly the same period technology growth when PC were in the 486 and Pentium Era. 700% increase in Graphics, 100% increase in CPU speed? When was the last time you seen any of these in PC.

    The next technological advance are in the Mobile / Phone space. They are the new PC. Just like how X86 manage to utilize its Desktop strength to gain market share in server space. May be ARM could finally dethrone x86. ( At least i hope so )
    Reply
  • iGo - Tuesday, July 7, 2009 - link

    Absolutely agree with cdrsft, never mind that guy. He probably read just the first and last page.

    Not always you come across the article which provides lot of information, on and off topic... and not always you find more than required information in an article which is actually useful and help you learn. Not to mention, all this written in absolutely enjoyable manner. :)

    Thank you, Mr. Shimpi for such wonderful article... and many more before this.

    Reply
  • cdrsft - Tuesday, July 7, 2009 - link

    never mind that guy - your article was great and very helpful for those of us who want to understand more....... thank you! Reply
  • bowtech - Monday, November 8, 2010 - link

    can u explain why cortex a8 did not beat arm 11 in almost any of these tests then.http://www.pengutronix.de/development/kernel/arm-b... Reply
  • MassiveTurboLag - Tuesday, April 30, 2013 - link

    By the look of that video screenshot Anand drives a Porsche Cayenne. I hope he didn't see Jeremy Clarkson's video on it. Reply

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