So is R580 supposed to be 48 pipes or 48 ALUs?

Discussion in 'Pre-release GPU Speculation' started by Bill, Nov 19, 2005.

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  1. Bill

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    http://www.theinquirer.net/?article=27805

    If it's pipes, seems they would have no problem "taking back the performance crown from Nvidia" as INQ says. So why phrase it like that?

    If it's ALU's, we get a good idea of X360 performance early. Which most excites me.

    Though it may be clocked 700 mhz.

    http://www.xbitlabs.com/news/video/display/20051111144411.html

    Also Xbit refers to them as "pixel processors" rather than pipes, which is odd.

    And another oddity, 8 vertex processors wouldn't seem to be able to support 48 pipes, but 48 ALU's maybe.
     
    #1 Bill, Nov 19, 2005
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  2. SynapticSignal

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    I think 48 Alu
    so 12 Shader core
     
    #2 SynapticSignal, Nov 19, 2005
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  3. SynapticSignal

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    #3 SynapticSignal, Nov 19, 2005
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  4. trinibwoy

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    48 shader cores, 2 ALU's each, one full, one mini ?
     
  5. Tim

    Tim
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    Yes and each ALU is to coissue 1 scalar and 1 Vec3 instruction.
     
  6. SynapticSignal

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    mmh appear to be different as ATI named the alu (alu 1 and alu 2)

    seems as scalar ALU 1 + scalar ALU 2 + vector ALU 1 + vector ALU 2 = 4 ALU
     
  7. Ailuros

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    4 quad "MIMD" (I'd actually call them 16 SIMD channels, but then I'll get corrected again LOL) and 48 ALUs.

    Not really comparable either, since Xenos has "general purpose" ALU units; 3* 16-way SIMD to be more precise.

    I'm not so sure Xenos is even faster than R520, let alone R580.
     
  8. Dave Baumann

    Dave Baumann Gamerscore Wh...
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    And that certaintly wouldn't work in this case.
     
  9. Kaotik

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    -delete-
     
  10. Megadrive1988

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    it seems R580 will be 16 pixel pipes, like R520 (both have 16 ROPs) but R580 will have 3 shader ALUs (or fragement shaders) per pipe, so that's where the 48 comes from.

    that's the explanation from me, a non-techie :)
     
  11. Jawed

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    R520 has four quads. Each quad has:
    • four texture pipes,
    • four shader pipes and
    • four ROP pipes.
    R580 also has four quads. Each quad has:
    • four texture pipes,
    • 12 shader pipes and
    • four ROP pipes.
    The shader pipes in both R520 and R580 consist of a primary ALU that can execute all maths instructions and a secondary ALU with minimal functionality.

    R580's 12 shader pipes in each quad take it in turns to use the texture and ROP pipes in the quad - four pipes at a time.

    Jawed
     
  12. Sunday

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    I don’t get it how some people on this forum failed to see from Dave article and the explanation of RV530 architecture what R580 will look alike. To totally simplify, R580 will be 4 times RV530, just like R520 is 4 time RV515!

    Word “Quad†in this context comes from grouping of four PS pipes, so you can’t really have “quads†with twelve pipes?! But what you can have is “twelve quad engines†– 12 sets of four PS pipes.
     
  13. tEd

    tEd Casual Member
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    Not quite. rv530 has 8 z units per quad. r580 has 4
     
  14. Pete

    Pete Moderate Nuisance
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    48 fragments shader units, each of which consist of one full and one mini ALU (arranged in four quads with 12 shader units per quad). So, multiple fragment ALUs per shader unit.

    AFAIK, Xenos also has 48 shaders (not specifically fragment), but they're differently arranged (three shader "pipes" with 16 shaders per pipe) and don't include the mini ALU. So, one ALU per shader unit, but the ALU isn't equivalent to something on R5x0.

    You'd be doing yourself a favor by not using The Inq--OK, Fuad specifically--for technical details of GPUs. :)
     
  15. R300King!

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    This is all fine and dandy but what performance % over the R520 will the R580 be?

    5% - 15%
    15% - 25%
    25% - 35%
    35% - 45%
    45% - 60%
    60% - 80%
    80% - 100%
    100%+
     
  16. Skrying

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    Depends HIGHLY on what game you're playing.
     
  17. KimB

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    There may be some very special scenarios where the performance improvement climbs to 100%. But most of the time it's going to be under 50%, is my guess.

    Edit:
    Of course, some pure ALU synthetic benchmarks may show the full 3x performance.
     
  18. Skrying

    Skrying S K R Y I N G
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    I think R580 will be locked at 725Mhz and 1800Mhz. I think we'll see around a 35% average increase and in some cases much higher.
     
  19. wireframe

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    Those seem to be some fairly optimistic numbers on the core clock. Maybe ATI can pull it off, but let's not forget how massive this thing is compared to R520. Even if they could pull that off, would they want to? You don't want to take away the incentives for purchasing the next generation GPU (yay, I said GPU for ATI instead of VPU...*erm*)

    The point here is that R580 is a step up in shading power. Technically, I don't think it needs a higher clock because what it proposes to do it will do through sheer parallelism. There is no way R520 can touch it and compete. It's in the clear, by design.

    Also, is it really interesting to think about those 35% improvements? That would be for current games and I think it safe to say that it will be for somewhat dated current games that have moderate shader usage. Perhaps something like Far Cry. The thing to keep in mind here is that those games run just fine on current hardware, R520 and G70, and I don't know that it is interesting to even pay attention to those 35% numbers. In newer, more shader heavy title, however, you should see a huge impact and I don't think it is stretching it to say that upcoming games that rely heavily on shaders will see a 100% increase in performance. Then again, those games will surely also scale to suit less endowed hardware and the question then becomes: are those effects that are made feasible with the new hardware worth it?

    Basically, what I am getting at here is that performance can no longer be incremental like back in the vertex & texture days. I think the next step in shading usage can be likened to going from wireframe graphics to solid fill graphics and then to high-resolution textured graphics. The first step, done, is just a "filler" (pardon the pun) while the next, adding textures, you either go all the way or you forget about it. It's going to be costly.
     
  20. KimB

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    How well it does will depend on the ALU to TEX op ratios. And let's not forget that texturing can take quite a while with anisotropic filtering.
     
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