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Xbox 360 GPU A Vector Co-Processor?

Posted by Zonk on from the number-crunching dept.

Anyone Seen Thomas? writes "While Beyond3D's article on the ATI C1 (XENOS) graphics processor in the XBOX 360 gives you all you need to know about ATI's next generation hardware in terms of generating screen pixels, it also gives a big clue as to how it'll be useful for general purpose vector programming. XENOS is able to write data out of its unified memory architecture into system memory, and read it back again later. So with a large pool of powerful vector hardware available, does anyone fancy the idea of having a generalised , high-performance vector processor in their PC?. Read about that and the rest of XENOS." From the article: "Since XBOX 360's announcement and ATI's unleashing from the non disclosure agreements we've had the chance to not just chat with Robert Feldstein, VP of Engineering, but also Joe Cox, Director of Engineering overseeing the XBOX graphics design team, and two lead architects of the graphics processor, Clay Taylor and Mark Fowler. Here we hope to accurately impart a slightly deeper understanding of the XBOX 360 graphics processor, how it sits within the system, understand more about its operation as well as give some insights into the capabilities of the processor."

37 of 55 comments (clear)

  1. Interesting... by alvinrod · · Score: 1
    In simple terms the MEMEXPORT function is a method by which Xenos can push and pull vectorised data directly to and from system RAM.

    The only problem is that if the GPU has to use the same bus as the CPU in which case they'll have to compete with each other, potentially leading to bottlenecks and/or messy bus arbitration. Hopefully Microsoft will give the GPU direct access to the memory.

    Performance-wise, it wouldn't be quite as good as having built-in memory on the GPU, but it will be a lot cheaper and have access to a lot of memory since the Xbox 360 is supposed to have 512 Mb of RAM.

    Kind of funny how both ATI and Nvidea are pushed more by console graphics developement now days than anything else. At least something is fueling better technologies.

    1. Re:Interesting... by Keeper · · Score: 2, Interesting

      The GPU also functions as the main memory controller; it has full access to all of the memory on the machine.

      MEMEXPORT is exceptionally cool because this means that the CPU can stream data to the cache and let the GPU access it directory. This reduces latency and yields more useable bandwidth for main memory for both the CPU and the GPU.

    2. Re:Interesting... by plaisted · · Score: 1
      Check out this page of the article. The XBox 360 uses a unified memory architecture, and the same 512 MB of memory is used by the CPU for general purpose use and the GPU for storing textures or whatever. There is also 10 MB of eDRAM which serves as a frame buffer which can handle some processing such as Z-buffering, blending, etc.

      The heart of the GPU seems to be on the same chip as the Northbridge controller, which basically means that the GPU has more direct access to the memory than the CPU.

      Check out the diagram on the page I linked, which shows the bandwidth between the various components. If there is any competition for memory access, I think it will be well balanced between the CPU and GPU.

    3. Re:Interesting... by Keeper · · Score: 1

      I look at it and I don't see how anyone with real world hardware experience can have your reaction.

      The design is brilliant.

    4. Re:Interesting... by Keeper · · Score: 1

      The original xbox design was meh. It was a brute force attempt at designing a console in a short period of time. It did bring some unique things to the console party -- an integrated hd and xbox live.

      Of course, I wouldn't expect someone with the mental capacity of a fish to be able to objectivly evaluate the situation, so feel free to continue trolling.

  2. Re:Now this is how you sell a console by vertinox · · Score: 2, Insightful

    Not like Sony's current stance of producing nothing of substance, whilst slagging off the competition.

    So is this a paid ad from Microsoft or just an independant review from a third party? I don't think they are trying to sell me anything other than an informative article.

    --
    "I am the king of the Romans, and am superior to rules of grammar!"
    -Sigismund, Holy Roman Emperor (1368-1437)
  3. Just an Example... by superpulpsicle · · Score: 5, Insightful

    Does anyone else think Gran Turismo 4 looks actually better than Forza sports? Point being, the console world is always 50% hardware, 50% software.

    1. Re:Just an Example... by alvinrod · · Score: 3, Insightful
      Don't you think that beauty is in the eye of the beholder? It's really a matter of opinion which game "looks" better. You can ask which has more polygons on screen at any given moment, in which case you could probably guess Forza and be correct, but that doesn't necessarily translate to looking better.

      I could make a car that takes all the processing power the the Xbox to draw, and still have it look like crap. I'm not saying this is the case with either game, but it's a valid point.

      The software is always limited by the hardware. You can't go beyond these limitations without having negative effects (i.e. framerate being terribly low, etc.).

      Looks are more or less dependent on the art style used by the game. This is what graphics should really be based around, rather than how many polygons can this console render at any given time. The next generation consoles (mainly the PS3 and Xbox 360) will be able to produce frighteningly large numbers of polygons at any given moment (the PS3 is supporting dual 1080p!) but that doens't necessarily mean the games will look any better.

      Personally, I'd like to see more along the lines of an 80% focus on Software. That and more gameplay and less graphics.

    2. Re:Just an Example... by Keeper · · Score: 1

      I don't. The difference between the two is the "character" of the graphics.

      Tracks: GT4 is "brighter" and more pleasant to look at, but isn't very realistic; for larger tracks GT4 is lacking detail/draw distance. Forza is "duller", but is a more accurate reproduction of the environments they're trying to re-create.

      Environment: Forza wins this one hands down; color reflections and accurate shadows are the big differences.

      Cars: A bit of a tossup; GT4 is better with some models, Forza is better with other models.

    3. Re:Just an Example... by Keeper · · Score: 1

      I don't. The difference between the two is the "character" of the graphics.

      GT4 has a "brighter" more pleasant look to some of its tracks, but isn't very realistic; for larger tracks GT4 is lacking detail/draw distance. The overall graphic quality hasn't changed much since GT3 IMO.

      Forza tracks are "duller", but is a more accurate reproduction of the environments they're trying to re-create (with the exception being the ring; it "looks" like the ring, but the layout isn't much like the real thing). Forza has proper color reflections and shadow occlusion.

      Forza's graphics are AA at a solid 30fps; GT4 runs at 60fps with no AA.

      Car models are a tossup; some are better in one game, some in the other. The cars in GT4 always seem overly shiny/reflective, which isn't the case in Forza.

      I personally like the graphics in Forza better than in GT4, but it really depends on your tastes and what kind of "candy" you prefer.

      The real advantage forza has is not the graphics, but rather the physics -- Forza is a much better sim than GT4 IMO.

    4. Re:Just an Example... by oGMo · · Score: 2, Insightful
      If anyone thinks anything else, they're just being silly. The video comparison on IGN between the two had me more suprised than I thought I'd be. At first I thought the GT4 screen was the XBOX game just because it was so much more realistic.

      This is why recently I've been comparing PS2 and XBOX games. XBOX stuff hasn't seemed to improve considerably. Compare various shots/videos of GT4, God of War, Metal Gear Solid 3, Haunting Ground, Jak3, and others to Halo 2, Forza, etc. and you'll be suprised: the PS2 is actually better looking!

      This is somewhat along the lines of what a few of us were saying years ago when the XBOX specs came out: the PS2 may seem to have smaller numbers, but it's a custom system, custom CPU, architected specifically for what it does. Give it a few years to mature and we'll be seeing things that still amaze us. The XBOX is just the same old Intel box; people already know how to get a lot out of it, so what you saw then was about the best you'd ever see.

      --

      Don't think of it as a flame---it's more like an argument that does 3d6 fire damage

    5. Re:Just an Example... by zero_offset · · Score: 1

      Make the same comparison on a large screen and you'll change your mind. Then turn on 480p or 720p in the Xbox games and you'll wish slashdot had UBB-style "Delete My Post" capabilities. :)

      Seriously, we have a 68" rear-projection TV in one room and a DLP front projector shooting a 92" picture in the HT room and PS2 games just look awful by comparison.

      --

      Slashdot quality declines as the number of hot grits posts decreases. - Provolt's Law, Apr-09-2005

  4. Re:Now this is how you sell a console by bigman2003 · · Score: 1

    Exactly-

    Real information, rather than "ours will be better." (because we said so)

    --
    No reason to lie.
  5. tech-specs are irrelevant by Anonymous Coward · · Score: 3, Interesting

    I know that both ATI/Microsoft and Nvidia/Sony really want to 'hype' their technologies but is anyone out there actually delusional enough to think that any of the upcomming systems ( XBox 360/PS3/Revolution) will actually produce graphics that are dramatically different from any of the other systems?

    To a certain extent I'm personally expecting very little in the way of technical progress in graphics and a far greater focus on artistic considerations. Let's face it, we're hitting a point where using 'brute-force' and dramatically increasing the geometry in your objects is not what will produce a better looking game; what will make a difference is well designed objects and a more populated environment.

    Now, more technical power is needed to obtain these more populated environments and can help with designing better objects but there is a limitation on what is currently needed. I expect that, for the most part, if you could produce 4 times the geometry of the XBox (twice the geometry per object and twice as many objects on screen) and you can have every pixel calculated by a shader (which is aproximatley 4 times as complicated as one that can be run on the XBox) you will be meeting the requirements of almost every game made in the next generation. I expect that every one of the upcomming consoles surpasses these specifications.

    1. Re:tech-specs are irrelevant by plaisted · · Score: 1
      Have you seen the screenshots for Elder Scrolls: Oblivion? To me the forests look amazingly better than anything else I've seen in a game. I think there's something like 8 square miles of them total. I believe it uses the CPU to procedurally generate the geometry. It's possible to generate this much detail dynamically because you can set it up where the CPU can write data to the cache and the GPU can read directly from the cache without having to go through main memory.

      Screenshot 1
      Screenshot 2
      Screenshot 3

    2. Re:tech-specs are irrelevant by KillShill · · Score: 1

      it's also coming out for the pc and with current gen gfx cards and with the imminent introduction of new cards, it'll run with no problems and will look just as good (it could look nicer if they took advantage of the pcs strengths).

      --
      Science : Proprietary , Knowledge : Open Source
  6. Re:Now this is how you sell a console by gabebear · · Score: 3, Insightful

    Honestly, I thought this was a slap at Microsoft. In the article they admit that the GPU is not compatable with DirectX. The original XBox's DirectX implementation was a bit funky but basically it was DirectX8 and developers bitched about that. The XBox360's Shaders(and who knows what else) aren't DirectX9 compliant, and it sounds like their is no hope for it Being DirectX Next compliant. If developers are going to have to rework a lot of complex code for the XBox360 I think this will turn off many game developers who see the XBox as a console that's cheap to port.

  7. Re:Now this is how you sell a console by justforaday · · Score: 1

    Correct me if I'm wrong (which I very well may be), but wasn't Microsofts big selling point to developers the fact that the original Xbox used DirectX, so development would be easy?

    --
    I'll turn into a supernova and burn up everything. Well I'll turn into a black little hole and you'll turn into string.
  8. Re:Now this is how you sell a console by gabebear · · Score: 2, Informative

    Yes, that was the point I was trying to make. Since this article says DirectX has been basically thrown out the window when designing the XBox360's GPU it will alienate a lot of the game developers that were drawn to the original XBox. Ports of Windows games will also need to rework all their SSE optimizations to altivec and make sure their code is big endian safe for the PowerPC CPUs.

    I have never written a game for the original XBox but I know you can't rely on DirectX8 completely for 3D. The XBox's 3D API is just strongly based on DirectX8. To utilize the XBox's console properties(like truly shared RAM) you have to use some extra libraries that Microsoft included in the XDK.

  9. Outsourcing? by alexo · · Score: 1


    > The GPU also functions as the main memory controller

    Cool.

    What's next? A floppy controller in charge of CPU to CPU communications?

    1. Re:Outsourcing? by Keeper · · Score: 2, Informative

      Think about it for a minute. What component in the system is going to be hitting memory the most? (hint: it renders textures to the screen) Look at what kind of bus that most PC video cards have between the GPU and on-card memory -- they're built to reduce latency as much as possible.

      Moving the memory controller onto the same die as the GPU yields a non-trivial performance benefit both in available bandwidth and latency (look at what kind of gains AMD got by moving the NB on-chip) .

      If the controller were on neither the CPU or the GPU, you end up with performance of both the CPU and GPU decreasing and higher production costs (more chips to produce/install and more traces on the board).

      If the controller had been moved onto the CPU, CPU performance would be better but GPU performance would suffer. CPU performance constraints can be reduced significantly by proper management of the L2 cache. However, caching for a GPU is not an effective stratedgy given that most of the bandwidth needed is either pushing rendered data out to memory (never to be read again) or pulling in data for textures. In other words, placing the memory controller on the CPU is not an optimal performance gain.

      Sticking that puppy on the GPU was definately the right decision.

    2. Re:Outsourcing? by chrish · · Score: 1

      You laugh, but in days of yore, the CPU inside the Commodore 64 disk drive (the 1571) was more powerful than the CPU in the C=64 itself.

      --
      - chrish
    3. Re:Outsourcing? by alexo · · Score: 1


      > but in days of yore, the CPU inside the Commodore 64 disk drive (the 1571)
      > was more powerful than the CPU in the C=64 itself.

      Actually, the 1571 came in 1995 (as a companion to the C=128), 3 years after the C=64.
      The step-up from 1MHz to 2MHZ during that time is to be expected.

  10. Re:PSP has at least 2 VPUs... by gabebear · · Score: 3, Informative

    The PSP's CPU architechture is VERY close the the PS2's, but the PS3 is a whole nother beast. The PS2 has 2 VPUs with 32 128-bit(4x32bit) floating point registers and 16 integer registers with 16KB of Data Memory. The main CPU is MIPs based. The PS3 uses the new CELL CPU which is PowerPC based, the CELL will use 7 SPEs that each have 128 128bit registers and each has 256KB SRAM.

    The PS3's SPEs will be used very sililarly to the PS2's SPUs(dot-products, etc) although they are much much bigger, there are a lot more of them, and they are a LOT faster. The CELL CPU was developed by Sony, Toshiba, and IBM and is slated to be put into TVs, PVRs, etc. It is very good at compression/decrompression, showed it off decoding 48 MPEG2 streams with power to spare.

    So the answer to your question is; not yet. Sony will put a CELL CPU in many of their electronics, but not until it is cheaper.

  11. what does this mean for apple on intel? by raistlin42 · · Score: 1

    So does this mean that apple can rewrite vecLib to take advantage of future vector processors? With a fast enough interconnect (PCIe?) this would be a viable replacement for altivec.

    --
    "My life is a joke that no one gets"
    1. Re:what does this mean for apple on intel? by javaxman · · Score: 1
      So does this mean that apple can rewrite vecLib to take advantage of future vector processors?

      This has nothing to do with that. Although, they can and are. They've been calling it the "Accelerate Framework" and it's been available ( well, most of it, I guess ) since 10.3. But we're not talking about a vecLib re-write. If you use vec_foo, you'll need to look for _mm_foo and re-write your own code. But vDSP, vImage, and other higher-level functions outlined on the linked documentation page, those should 'just work', as long as there's supported platform to target, as likely will be the case for Intel chips moving forward...

      Altivec-optimized code is going to be the single largest issue for programmers in the switch to Intel. Meaning, it's actually going to be a pretty darn smooth transition for most.

  12. Re:Now this is how you sell a console by zero_offset · · Score: 2, Insightful

    You're right, but you're overlooking an important point. Xbox developers basically didn't think DX/D3D compatibility was especially important. It was a selling feature that Microsoft hoped would score big, but that didn't happen. The 360 apparently has an all-new 3D API which was created in concert with some of the largest Xbox developers.

    Anybody with even a little 3D programming experience will tell you that it isn't too difficult to learn a new API. They all deal with essentially the same concepts.

    --

    Slashdot quality declines as the number of hot grits posts decreases. - Provolt's Law, Apr-09-2005

  13. Re:Now this is how you sell a console by gabebear · · Score: 1

    You are correct, DirectX was over looked by the majority of XBox developers. I think this is because most console games are developed with game engines and frameworks that have already been ported to each console. However, many of the XBox exclusive titles are ports from Windows; i.e. Counter Strike, Star Wars KotoR, Star Wars Republic Commando, and even Halo.

    While DX/D3D had little impact on most of the games released for the XBox, it probably did have a large impact on exclusive titles. Exclusive titles are one of the main reasons to buy one console over the other.

  14. Ok, I'm the dumb one here by lion2 · · Score: 1

    Can someone explain to me what a vector processor is and what is it good for?

    --
    #####Free and Open Source Game Directory#####
    1. Re:Ok, I'm the dumb one here by gabebear · · Score: 1

      Doing vector proccesses of course...

      You use them when you want to apply one operation to a set of values very quickly, you can think of them as bulk data CPUs. They are very fast at recalculating 3D coordinates, antialiasing images, and lots of other stuff.

    2. Re:Ok, I'm the dumb one here by Cymage · · Score: 1
      Wikipedia is your friend:

      Vector Processor

  15. Re:So XBOX 360 GPU is a cheap ass embedded process by KDR_11k · · Score: 1

    So, when the XBox uses PC parts people complain that it's just a PC, when it uses custom parts meant for embedded devices (e.g. consoles) everybody complains that MS is using cheap parts? What do you want, a 500$ chip? Would you pay 1000$ for a console?

    --
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  16. You mean like a DSP chip, perhaps? by javaxman · · Score: 1
    does anyone fancy the idea of having a generalised , high-performance vector processor in their PC?

    Yea, occasionally I'd like one, but I'd rather it didn't take away from what my graphics card can do, wouldn't I ?

    Like, maybe I'd like to have a generalized DSP chip like the one in my NeXT machine here, or one of these specialized DSP boards ?

    But if you want a GPU that's targeted to supporting DirectX, I don't know if using it for a DSP is really the right idea. Maybe it is. Or maybe Intel's own vector processing capabilities could improve. Or maybe you could get an extra board and actually make use of those empty, fast PCI slots. Your call. TFA does a good job of pointing out that GPUs aren't exactly 'general purpose', and that's why the article contains :

    why aren't we seeing it in the PC space yet? Xenos's particular range of features are going into a closed box environment, hence the API can be tailored to expose all of the features of the chip, however on the PC space graphics processors really need to be tailored to the capabilities of the current DirectX release. This is where Xenos has an issue in that its features and capabilities are clearly beyond the current Shader Model 3.0 DirectX9 specification while it lacks features that are expected to be a requirement for WGF2.0.

    So, what's the story even talking about here? Something that's possible except for Microsoft? Or something that's possible, in a completely different form? What's the point they're trying for?

  17. Re:Now this is how you sell a console by gabebear · · Score: 1

    Ah, but nothing Microsoft has put out about XNA says jack about this discrepency. If you are developing a game for the XBox360 and Windows in parallel I'm sure XNA will work well. If you have already developed your game for Windows without giving any thought to the XBox360's hardware limitations then it's going to be a giant pain in the ass to port to the XBox360, it may be easier to port to the PS3.

  18. Re:Now this is how you sell a console by S3D · · Score: 1
    Anybody with even a little 3D programming experience will tell you that it isn't too difficult to learn a new API. They all deal with essentially the same concepts.
    It's not difficalt to switch API and use a new API for a new product. However porting finished product from one API to another present a lot of non-trivial problem, mostly due to unexpected driver-specific side effects, especially if coupled with porting to another OS. (I had expirience of porting quite a big project form DirectX to SGI OpenGL)
  19. Re:So XBOX 360 GPU is a cheap ass embedded process by Pranadevil2k · · Score: 1

    Nobody is complaining that the parts are cheap. They're making the point that Microsofts consoles video card is using API software FAR removed from Microsofts proprietary DirectX stuff, which was originally created to be a unifying graphics architecture....

  20. Re:Now this is how you sell a console by zero_offset · · Score: 1

    Good point.

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    Slashdot quality declines as the number of hot grits posts decreases. - Provolt's Law, Apr-09-2005