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Ati R300 Vs Nv30

Discussão em 'Novidades Hardware PC' iniciada por JohnnyM, 19 de Novembro de 2002. (Respostas: 0; Visualizações: 515)

  1. JohnnyM

    JohnnyM Power Member

    Differences between the chips
    As I said before, I've read up on both chips and talked to folks from both NVIDIA and ATI in an attempt to understand the similarities and differences between these chip designs. Both designs look very good, and somewhat to my surprise, I've found very few weaknesses in the ATI design, despite the fact it's hitting the market well before NVIDIA's chip. There are some differences between the chips, however, and they point to different approaches taken by the two companies. Most of my attention here is focused on the pixel pipeline, and the pixel shaders in particular, because that's where the key differences seem to be.

    For what it's worth, I've boiled down those differences into a table, which does a nice job of encapsulating the issues for us. As is often this case with chips this complex, sticking the specs into a table can't do them justice at all. I realize this is a gross oversimplification, and I'm probably totally missing the boat on vertex shader implementations and various other things. But I'll persist, because I think the table is instructive.

    ........................................=R300=---------------------------------=NV30=
    Pixels per clock..........................8---------------------------------------Unknown
    Textures per pipe per rendering pass......16--------------------------------------16
    Textures per pipe per clock cycle.........1---------------------------------------Unknown
    Texture address operations per pass.......32--------------------------------------1024
    Color instructions per pass...............64*-------------------------------------1024
    Max pixel shader precision................96-bit floating point-------------------128-bit floating point
    Integer color modes.......................16, 32, 64 bits (signed or unsigned)-------16, 32 bits
    FP color modes............................16, 32, 64, 128 bits--------------------64, 128 bits
    RAMDAC precision..........................10 bits/channel-------------------------10 bits/channel
    Early Z occlusion culling?.......................Y--------------------------------Y**
    Pixel shader ops on video streams?...............Y--------------------------------Y
    Max parallel configuration.......................256 chips------------------------Unknown



    *Up to 128 instructions are possible with carefully arranged data and the use of swizzle
    **NVIDIA won't confirm this one, but one of their Siggraph presentations mentions Early Z in next-gen hardware

    NVIDIA isn't filling in all the blanks for us yet about the NV30, but we have enough information to see that NV30 allows for the execution of much longer pixel shader programs in a single pass. Now let me give you my qualifications of the above table, and then we can talk about the implications.

    First, I may not have a complete set of color modes listed for the NV30. I actually expect it to support all the modes I've listed for the R300, which ATI says are all part of the DX9 specification.

    Next, I've listed the NV30's potential for working in multi-chip solutions as "unknown," but NVIDIA would confirm for me that they plan to continue to support Quantum 3D, who ships multi-chip products now based on current NVIDIA chips. I'd expect to see multi-chip NV30-based solutions of this class, as well.

    Also, NV30 has long been rumored to have eight parallel rendering pipelines, as R300 does. This configuration only makes sense, and I'd be surprised to see NV30 have fewer than eight pixel pipelines.

    Note that NV30 can, like the R300, apply pixel shader effects to video streams. This capacity changes the image processing and video editing games, because Photoshop-like effects can be applied to incoming video streams in real time.

    Finally, I've not included any numbers on memory bandwidth here. The Radeon 9700 will launch with DDR memory and a 4-by-64-bit memory interface capable of moving about 20GB/s of data. ATI claims the R300 can address DDR-II memory types, as well. NVIDIA will only say that NV30 can use "DDR-II-like memory." Use of DDR-II type memory has the potential to double memory bandwidth from the current 20GB/s, but only time will tell how this one will play out.




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