AMD: R7xx Speculation

Discussion in 'Architecture and Products' started by Unknown Soldier, May 18, 2007.

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  1. Jawed

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    If ever there's a game to test on HD4870X2, it would seem to be Racedriver GRID. From the FAQ:

    http://community.codemasters.com/forum/showthread.php?t=279124

    Jawed
     
  2. Mintmaster

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    I'm going to have to disagree here. Of all PC architectures, RSX was by far the best at the time for the size. Nothing based on G80 (which was too late anyway) would be any faster unless you heavily modified it. G84 is the closest in size and transistor count to G71 (remember that the former is 80 nm), but far slower.

    Xenos stands out because it was designed from the ground up for a console. It has a high setup rate (not useful on the PC in 2005), can get away with EDRAM (128-bit bus no longer hurts perf), there's no need to build a scalable architecture (no wasted trannies on making 4 smaller units instead of one big one), etc.

    First of all, you have to realize that R600's shortcomings are all related to perf/mm2, not the relatively useless metric of perf/pipeline.

    R600 really is quite different. There's a radically different memory system (which they sort of ditched now) and far different shader structure (Xenos had one scheduler and one texture unit block, R600 had 4), texture filtering unit (R600 spent mostly useless trannies here), DX10.1 and PC related extras, and maybe going from 4D+1D to 5x1D w/integer originally took a lot more transistors than it should have.

    True, but for pixels shader loads there's no reason to think it's closer to R600 than R580, and the latter's decent in terms of efficiency by even RV770's standards (but not unified or DX10, of course).
     
  3. Jawed

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    High quality version is worthwhile

    http://www.youtube.com/watch?v=ROAJMfeRGD4&fmt=18

    Yeah he seemed to be saying they have a variety of maps, which are static.

    Rendering, though, appears to be voxel-based ray-tracing with wavelets used to compress the voxels - running in real time. The whole thing is ray traced, there is no triangle-z-buffer based rendering. Seems pretty unbelievable...

    Jawed
     
  4. trinibwoy

    trinibwoy Meh
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    So what exactly is "static" in that scene?
     
  5. MfA

    MfA
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    You can "rasterize" voxels too (splatting).
     
  6. Jawed

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    Are you talking about objects or computed data?

    Clearly most objects are static: the buildings (except for the bits that get knocked off), the cars (except for the taxi, those at the crossroads driving left-right and the car that escapes being crushed) and the road (except for the odd crater and debris) and the sky (which appears to be changing during 1:33-1:39 in the video, it looks like reflections of the sky on the cars are changing).

    As to whether the "global illumination, photon maps, diffuse lighting" are static, well I dunno. Seems likely.

    The way some transitions of rendering type occur, it looks like rendered results are cached for re-use in later frames.

    Jawed
     
  7. Mintmaster

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    Yup, I like it too. That's why I thought that similar-looking sliver next to the 4x10 array was redundancy, but then mczak pointed out that it looks a bit different. hoom's explanation tells us why - only the bottom half needs to look the same for the theory to work.

    I guess instead of 25.2% or 28%, it's really 26.6% devoted to the ALUs. Eerily similar to the 26.5% that Arun concluded for GT200. :smile:

    Now the only thing preventing a true apples to apples comparison of ALU density is the scheduling logic.
     
  8. Jawed

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    So, if we take the "17 ALUs" that hoom has identified, we get 2.67% of the entire die. So that's 6.8mm2 for 120GFLOPs, or 17.6 GFLOPs/mm2, including the register file.

    If we include what hoom reckons is the sequencer, then we have 8.7mm2 (3.4% of the die), which gives 13.8 GFLOPs/mm2.

    Note that the most recent "big" picture of the die indicates that it is non-square, the height is 98.4% of the width...

    Jawed
     
  9. fellix

    fellix Hey, You!
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    It really looks convenient for a redundancy part, but it's somewhat too disproportional to me. :roll:

    The fact is, that the whole ASIC is really very dense design and that last X-Ray micro-graph just don't have enough resolution to dive in more detailed dissection.
     
  10. digitalwanderer

    digitalwanderer Dangerously Mirthful
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    How did Guru3D get it working? Any ideas on what Hilbert did? I'm perma-banned from there so I can't ask and my buddy who wants to know says they've disabled registration. :(
     
  11. Silent_Buddha

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    Amazing I remember the first voxel based game I played (Commanche) back in the DOS days and thinking how much potential it had if only they could get it to the point where the voxels weren't so darned big.

    I wonder if some innovative/daring game designer will attempt a Cinema 2.0 (no polygon) based game.

    If they have the budget for I'd think Adventure games would be perfect for this as they don't rely on speed. This is, of course, assuming Cinema 2.0 would be too slow for a FPS type of game, and possible even too slow for real time RPG or RTS.

    Then again probably not unless Nvidia hardware can do it also.

    Regards,
    SB
     
  12. Jawed

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  13. AlphaWolf

    AlphaWolf Specious Misanthrope
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    Here ya go
     
  14. mboeller

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    What about image based rendering like pixelplanes?
     
  15. AlexV

    AlexV Heteroscedasticitate
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    They fixed it with the latest 1.1 or whatever patch, and IHVs should have profiles in their drivers already. ATi scales to 2 GPUs but not beyond, with the 1.1 patch and latest drivers, about nVidia I have no idea. And even prior to the patch with some renaming you could get it to scale.
     
  16. Jawed

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    I've got no idea. He says very little during the 3 minutes, so I'll guess we'll have to wait for the real launch next week.

    Let's hope they don't hold this stuff back for X2' launch.

    Jawed
     
  17. thatdude90210

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  18. SimBy

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  19. Jawed

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    Note to SimBy (whose message got trashed). Yeah, seems those Grid developers really were living in oblivion to make that statement and then for everything to change. Bizarre.

    I dunno it actually makes me wonder if some studios actively avoid dealing with the IHVs.

    Jawed
     
  20. randomhack

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    About the new hotfix for 4800 series: does anyone have information about whether its faster than the earlier version?
     
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