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2x 5970's and Crossfire

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  • 2x 5970's and Crossfire

    I'm running into some trouble. At this moment I am running on 1 of 4 VPU's which is very frustrating. I've done some searching and tried setting up a chain and enabling it, but all I get is an error saying the platform is not supported. When I reboot, and check the Crossfire status, it is disabled.

    There is a message saying it could be enabled via P2P and GART so I did some more googling and found nothing about it.

    Any suggestions?

  • #2
    Motherboard = MSI 890GXM-G65
    Catalyst = 10.7
    OS = Linux Mint 9 Isadora 64b (based on Ubuntu)
    Cards = 2x Sapphire ATI Radeon HD 5970 in Crossfire config (bridged)

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    • #3
      Last I heard Crossfire required - as far as I understood - per-application profiles which really only exist on Windows. I'm not really sure whether it makes much sense to use that kind of a setup for gaming outside Windows. For GPGPU it would probably be quite awesome though. (and even there as two separate cards, not a Crossfire setup)

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      • #4
        Originally posted by nanonyme View Post
        Last I heard Crossfire required - as far as I understood - per-application profiles which really only exist on Windows. I'm not really sure whether it makes much sense to use that kind of a setup for gaming outside Windows. For GPGPU it would probably be quite awesome though. (and even there as two separate cards, not a Crossfire setup)
        I think it should be possible to do multi-GPU rendering in a generic way (although probably not optimally).

        A simple way would be to have both cards have the same data in memory.
        For each rendering operation, divide the target in two regions (ideally in a tiled pattern), and have each GPU render one region and send results to the other (so they end up with the same final surface).

        Vertex shading should be parallelizable too by using stream out with a similar strategy. You could possibly even use a geometry shader to directly send triangles to the right partition in this case.

        No open source driver does that though as far as I know, but fglrx seems to have at least some support for Crossfire.

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        • #5
          Originally posted by Agdr View Post
          I think it should be possible to do multi-GPU rendering in a generic way (although probably not optimally).
          Could in theory be done and can be done with current driver implementations aren't the same though. Yes, fglrx does "support" Crossfire as in I've read of it being able to recognize Crossfire setups but never heard of anyone actually managing to use it in some program.
          But as said earlier, GPGPU using eg Stream SDK or so probably benefits of having two cards regardless of Crossfire.

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          • #6
            You must be out of your mind to run CFX in Linux, fglrx is a lie.

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            • #7
              Originally posted by nanonyme View Post
              But as said earlier, GPGPU using eg Stream SDK or so probably benefits of having two cards regardless of Crossfire.
              Right. Crossfire refers to two or more GPUs working on parallel on a single graphics workload. All of the other multi-GPU scenarios are "not Crossfire" :

              - switching between discrete and IGP graphics depending on workload & power state

              - multiple GPUs running compute

              - multiple GPUs, each driving a different set of displays

              etc...
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