The New and Improved "G80 Rumours Thread" *DailyTech specs at #802*

Discussion in 'Pre-release GPU Speculation' started by Geo, Sep 11, 2006.

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  1. Jawed

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    Because of Xenos's support for 8 concurrent render states I think it's highly likely that later WDDM functionality for concurrent render states will be in R600. It could be only partial support, since WDDM functionality seems to be more general than what's in Xenos.

    I dunno enough about concurrent render states to know if a GPU can safely overlap render states while doing DX9 work (which would further decrease the "call overhead" that DX9 suffers with).

    Jawed
     
  2. Razor1

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    :lol:
     
  3. Geo

    Geo Mostly Harmless
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    Neither do I. I was just pointing at one explanation for why sometimes high-end cards have good initial availablity at launch, and then dry up for a bit.
     
  4. PeterAce

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    Architecture effecncy improvements and a leaning toward higher floating-point Pixel Shader performance that the IHVs are aiming for with these new gen GPUs for D3D10 surely will also help out in DX9.

    Whats good for the gouse is good for the gander? (wow... that last part was geo-like!).
     
  5. trinibwoy

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    I find this hilarious. You're basically saying G80 = G71 + change-everything-in-G71 + more features :lol: You can't improve everything about a chip and then say the result is old-chip + stuff. This whole unified shader thing is really reshaping everyone's opinions of what a new architecture should look like.
     
  6. trinibwoy

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    I'm not sure I follow this. What does "decided edge in DX10" really refer to? Synthetic geometry shader tests and the like? It seems that whoever is faster in the early DX10 titles will also be faster in the latest DX9 titles. The demands aren't going to change much - it's still going to be about high shader and memory performance.

    Unified shading hardware isn't something that magically improves DX10 performance simply because the APi is unified. If it works it will work just as well for DX9.
     
  7. _xxx_

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    I think geo is implying that nV will have some disadvantages in DX10 because of the architecture, which will favor the DX9 stuff more and the opposite for ATI.

    My guess is (I feel the flames rising already...) that G80 will stomp all over R600 in everything but a few synthetic tests. Based solely on my gut feeling and no facts at all.
     
  8. trinibwoy

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    I got that bit. But I guess what I'm asking is what is it about DX9 that could possibly facilitate that advantage. I can't think of any (dis)advantage that a unified design may have in DX10 that won't also translate to an (dis)advantage in DX9. Really looking for some insight here .....
     
  9. _xxx_

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    Just from the top of my head, I guess a "real" unified DX10 architecture will work with DX9 content through some sort of wrapper. That in itself would slow it down significantly if it's the case. And writing new drivers from scratch has it's pains as well.

    EDIT: as well as benefits like getting rid of the legacy stuff, so who knows?
     
  10. trinibwoy

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    Hmmm I don't know. Wouldn't any wrapper approach be at the driver level and affect any DX10 hardware - unified or not? It's the driver that has to translate APi calls into hardware instructions so I don't see why extra overhead will only apply to a unified architecture. It's not like Nvidia gets DX9 for free with G80.

    But since I don't know anything about this stuff I might be completely off :)
     
  11. nelg

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    Wasn't there a quote from someone at ATI that mentioned that the Xenos was faster than an equivalent (# of shaders) non-unified design?

    edit. found it.

     
    #151 nelg, Sep 13, 2006
    Last edited by a moderator: Sep 13, 2006
  12. Jawed

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    No different from G71 being better at backward-looking TMU-intensive pixel shaders and R580 being better at forward-looking ALU-intensive shaders (as well as dynamic branching).

    The "advantages" that R580 has for SM3 code are still barely relevant in current games. Whilst R580 does generally show better performance than G71 (at least in the most popularly benchmarked games/resolutions with high-AA/AF), there are no laurels for R580's theoretical advantages. No sign of any, either.

    Yeah, R600 is prolly on a hiding to nothing if it ends up touting the highest (or significantly higher) SM4 performance, because we won't have any games to enjoy that with, or they'll be limited options, e.g. like z-feathered smoke in CoD2. SM4 prolly won't be a compelling option for gamers till R700 hits...

    That didn't happen with the SM1.x-to-SM2 transition.

    But DX9 games tend to play to G71's strengths, which exclude intensive ALU code and dynamic branching - two features of SM3 that are barely capitalised-upon. So how's SM4, which is more of the same (and ignoring D3D10's architectural wonders that won't generally be in games for another 18 months), going to magically transform games whose SM2/3 performance is mainly bandwidth-bound?

    G80 is prolly going to be better at texture-intensive stuff than R600. The signs are that R600 will have no more texturing capability than R580. Whereas it's considered unlikely that G80 will have merely 24 filtering TMUs. If R600 measures better at ALU-intensive shaders, is that going to make any real difference to SM2/3 games? R580 hasn't benefitted dramatically.

    The other side of the coin with texturing, for example, is how effectively do the competing architectures use available bandwidth? If texture filtering quality is mandated by M$ (reduced angle-dependency, minimal brilinear artefacts, etc.) are we likely to see a more-level playing field? Does ATI's experience with the ring-bus, out-of-order threading etc. mean that second-generation texturing in R600 will have a significant advantage per byte of bandwidth?

    The other main factor in DX9 performance/configuration differentiation between G80/R600 is the ROPs. ATI is obviously ahead now, but NVidia is making noises about spending way more transistors (or at the very least going an extra generation forwards in terms of features) in the next generation, while ATI will prolly be consolidating based upon what's in R5xx.

    It might end up that with games commonly TMU-/bandwidth-/ROP-bound, efficient texturing or ROP will be all that sets the two apart. Nothing at all to do with D3D10 or unification. If one architecture spends significantly more transistors on texturing or ROP to the detriment of D3D10 performance, while the other architecture reverses those priorities, aiming at performant D3D10 features, then it seems there's a strong case that DX9 performance will be no indicator of D3D10 performance.

    Still, it'll be fun to talk about these architectures and being in PCs we'll have plenty of ways to play with them and compare, unlike the mostly locked-away Xenos.

    Jawed
     
  13. Jawed

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  14. LeStoffer

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    Indeed.

    Oh no, not again! :wink:
     
  15. trinibwoy

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    Yes, but that comparison is using the same API - which is exactly what I'm saying. That if unified is faster that discrete on DX10, it should also be faster than discrete on DX9.
     
  16. trinibwoy

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  17. Razor1

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    Unified should be faster if the same amount of calculations can be done both discrete or unified theoretically, only in ideal situations will a discrete match a unified (aslong as the overhead of the scheduler for unified is low).
     
  18. trinibwoy

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    I'm getting a bit lost in the DX10 comparisons. When people say DX10 performance are they referring to new functionality or "more widespread use of DX9 functionality that was ignored by developers last generation" ?

    Well in that context DX9 and DX10 aren't any different. Developers can choose to write TMU intensive shaders in DX10 as well. So I still don't see how a design can be inherently faster in one API while slower in the next.

    We all know it's not that simple. SM2 asked very different questions of the core shader pipeline than SM1 did and Nvidia failed to answer - DX10 and DX9 are not as different in that regard. So that's not going to happen unless G80 is NV30 part deux.

    Honestly, that makes no sense. Texture workload is obviously going to increase in the future. ATi is not going to design an inherently bottlenecked architecture that blazes through arithmetic and waits idly by for TMU's to do their thing.

    What do ROP's have to do with DX9/DX10 differentiation? I'm asking a serious question here.

    It's stuff like this that keeps me continually confused about what people mean by D3D10 performance. It comes across as if texturing and ROP/AA performance are not also DX10 considerations !! :???: These aren't legacy operations that are going to the wayside next generation - they are going to be ever present and just as important as before.
     
  19. ERK

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    The presumed 16 additional point-sampling TMUs would surely add something as well, no?
     
  20. Razor1

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    Die size, 2 cm x 2 cm:edit, sounds right it would be around 400 mm double the die size of the g71

    Dx 9 performance is very fast: expected

    12 memory chips: Rumor bin, was stated here

    1/3 of its die size is for dx 10 functionality: around 120-166 million tranis if it is a 500 million trani chip sounds about right. (gotta account for pure video)

    The rest of it is all pure speculation. Probably because of the 1/3 of die size is for dx10 operations. In Fuad's mind must of drew a few lines were dx9 and dx10 can't overlap. Of course dx10 performance will be poor if the g80 was designed with distinct dx10 portion and a dx9 portion, but it would be stupidity beyond believe if nV would try such a thing as they did with the fx.
     
    #160 Razor1, Sep 13, 2006
    Last edited by a moderator: Sep 13, 2006
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