NVIDIA GT200 Rumours & Speculation Thread

Discussion in 'Architecture and Products' started by Arun, Feb 10, 2008.

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  1. XMAN26

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    OK, are you saying each MC is 64bit wide and connects to 2 mem chips each? The card is reported to have 16 chips for 512bit bus.
     
  2. fellix

    fellix Hey, You!
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    Sixteen 32-bit devices would fill eight 64-bit channels -- the same case as in R600.
     
  3. ShaidarHaran

    ShaidarHaran hardware monkey
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    Yes. NV has used this approach since the original Geforce DDR days, IIRC. Crossbar w/64-bit channels FTW.
     
  4. Arun

    Arun Unknown.
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    Global Scheduler, Triangle Setup, Input Assembly, Rasterization, L2 Cache, I/O controllers, and so forth presumably - it's really just everything that isn't duplicated elsewhere on the chip.
    The I/O interfaces, yes, that's what you see on the edges of the chip.
    That's not cache; it's RF/Shared Memory. As for the amount, everything in due time...
    Yeah, it does, but I don't think there's anything revolutionary there that you couldn't notice from CJ's shot. Should even be possible to figure out what's copy-pasted and what's not. Alternatively, you could just wait for our article... As for when it'll come out, stay tuned! (Hi NV! ;))
     
  5. nAo

    nAo Nutella Nutellae
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    Hi-Z culling is probably a part of this chunk too then.
    Very interesting Arun, thanks for the info and I am waiting for the final article, harry up! :wink:
     
  6. Jawed

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    So, what we're seeing here is that 3 multiprocessors are about the same size as 4x TAs and 8x TFs.

    Hmm, so in G80 it's reasonable to say that 4x TAs+8xTFs+L1-cache are roughly 50% bigger than the cluster's ALUs+register-file+shared-memory ("16 ALUs"). Needless to say I feel vindicated after all the shit I've taken for suggesting that TMUs are costly.

    A naive averaging, 364M transistors across 80 bilinears per clock, makes each bilinear result cost ~4.6M transistors.

    Or if you prefer 40x fp16s, each of which costs ~9M transistors.

    Jawed
     
  7. Vincent

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    Any justification on why NVIDIA expands more TMU units within this brand new ASIC ?
    :?:
     
  8. Jawed

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    NVidia's bumped up the ALU:TEX ratio quite considerably. If they'd used less clusters (hence less TMUs) and more multiprocessors per cluster (to end up with ~900+GFLOPs) the ALU:TEX ratio would have gone up even more.

    For NVidia the meaning of ALU:TEX ratio is different than for ATI - I think it's reasonable to say that NVidia's thread scheduling (ALU and TEX instruction issue) means that a lower ratio is required to hide texturing latency.

    But, with the magically-rediscovered MUL the effective ALU:TEX ratio goes up another notch (though ALU clock of ~1300MHz and TMU clock of ~600MHz makes for a slight lowering of the ratio in comparison with G80's 1350/575).

    Anyway, in terms of overall performance I expect GT280's "80 TMUs" look "better balanced" than G80's 64 :wink:

    Jawed
     
  9. nAo

    nAo Nutella Nutellae
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    You are assuming that TMUs and SPs have not changed much from G80 to the new architecture, and at this time we really don't know.
     
  10. Jawed

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    The GT280 die picture makes this picture easier to interpret:

    http://www.techpowerup.com/reviews/NVIDIA/G80/images/core.jpg

    The extent of the ALUs is a bit hard to discern though, due to the way those sections fade at the edges. It seems the entire stretch of die between the multiprocessors on either side is TMUs. G80 doesn't have the "cross" that we see in GT280 - instead it seems to have 3 horizontal bands - apparently leaving the central region to TMUs.

    It seems G80 clusters are 50:50 multiprocessors and TMUs.

    Jawed
     
  11. 3dcgi

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    It usually takes more than 3 months to go from tape out to production.
     
  12. juan789123498

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    Is today, die shot's day?

    Ok, i will contribute with a G80 die shot, that even babies will understand.
    Jawed it's a little easier to discern blocks with this picture , no? :lol:

    [​IMG]

    And yes, G80 clusters seems to be 50:50 multiprocessors and TMUs.

    And I almost forgot to say I saw shared memory per multiprocessor gets doubled in GT200 vs G80 (32KB vs 16KB). And remember there are 30 multiprocessors vs 16 in G80.
     
  13. jimmyjames123

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    Arun, did you mean 13.0% for unique?

    Great breakdown, and even though you guys have a better shot, CJ's die shot was very nice!
     
  14. satein

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    So, is there any part refered to PV2 on this core :?:

    Don't tell me that the same history as G80 will repeat itself on GT200 too. :twisted:
     
  15. trinibwoy

    trinibwoy Meh
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    Well at least a doubling of the PDC was expected given the double precision support.
     
  16. dnavas

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    Is it really rediscovered, or has the marketing department "rediscovered" it?

    -Dave
     
  17. CJ

    CJ
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    The documents talk about "Improved Dual Issue"... so make of it what you will.... Also mentioned are "2x Registers" and "3x ROP blending performance".
     
  18. Anarchist4000

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    Sounds like they just fixed the MUL issue by adding register space and made a marketing issue out of it. I guess it could be viewed as discovered since it wasn't really available for general use, even through they counted it towards performance.
     
  19. AnarchX

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    According to a Mod from known PCinlife, who has also die-shots and other informations in his hands, GTX 280 will offer 2 times 8800 Ultra performance.
     
  20. Tchock

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    Last I heard, 2*9800GX2 performance came from their mouths too. :grin:
     
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