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Thread: Crossfire and AMD card owners - query on swapping PCI E priority and Powerplay clocks

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    Crossfire and AMD card owners - query on swapping PCI E priority and Powerplay clocks

    Two things I am looking to understand with AMD cards :

    A) If your motherboard has no BIOS setting /option for it, can you force the system to use the GPU in your second (or third) PIC E slot, as the primary display adapter? I have been unable to find such a feature in CCC, Radeon PRO or Afterburner.
    I can confirm that my system will display from a card in the second PCI E slot. It's when I install a second GPU back into the primary slot(near CPU) that it switches the display adapters.

    B) Is Powerplay (dynamic clocks/clock speed) meant to work in Crossfire mode? It works fine in single GPU configuration.



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    Last edited by Tester68; 22-03-2015 at 11:56 AM. Reason: Solved

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    Re: Crossfire and AMD card owners - query on swapping PCI E priority and Powerplay cl

    Just to clarify on point B).
    It's not about Powerplay 2d/3d clocks at the desktop. Rather it's about dynamic clocks when in a full screen mode. During single GPU setups, the clocks rise and fall according to GPU workload. However in Crossfire/multi gpu mode, this feature stops functioning.

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    Re: Crossfire and AMD card owners - query on swapping PCI E priority and Powerplay cl

    Quote Originally Posted by Tester68 View Post
    Two things I am looking to understand with AMD cards :

    A) If your motherboard has no BIOS setting /option for it, can you force the system to use the GPU in your second (or third) PIC E slot, as the primary display adapter? I have been unable to find such a feature in CCC, Radeon PRO or Afterburner.
    I can confirm that my system will display from a card in the second PCI E slot. It's when I install a second GPU back into the primary slot(near CPU) that it switches the display adapters.

    B) Is Powerplay (dynamic clocks/clock speed) meant to work in Crossfire mode? It works fine in single GPU configuration.



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    A) I think so, try plugging in the monitor to the gpu you wish to use. If it does not work correctly then use slot one.

    B) Yes powerplay should work as normal in Crossfire mode. Unless you disable ULPS then the second gpu should turn off completely when the pc is in 2D mode or idle. Once 3D starts it should kick in.
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    Re: Crossfire and AMD card owners - query on swapping PCI E priority and Powerplay cl

    Quote Originally Posted by AMDMatt View Post
    A) I think so, try plugging in the monitor to the gpu you wish to use. If it does not work correctly then use slot one.

    B) Yes powerplay should work as normal in Crossfire mode. Unless you disable ULPS then the second gpu should turn off completely when the pc is in 2D mode or idle. Once 3D starts it should kick in.
    Hi Matt,

    Fortunately these cards and the motherboard, will respond by doing as you said - plugging in the monitor to the second card. The key is to do this with that one and only card installed. Boot to Windows then shut down. Install the second GPU in the first PCI E slot. Windows will still treat the card in slot two, as the primary. Then you enable Crossfire and reboot again.

    You lose the ability to see POST/BOOT, but it's a fair work around for motherboards that do not support PCI E boot priority settings.


    My apologies, I was not talking of Powerplay 2d/3d clocks. I meant to say dynamic clocks - which after a discussion with AMD, this is not supported in Crossfire.
    So please Matt, tell someone at AMD that I'd love that feature in their next cards. There should be two modes :

    A) Auto
    B) User controlled

    In auto, the system decides whether to use dynamic clocks on both cards, or one card (and also which of the two)
    In user controlled, the user decides whether to force dynamic clocks on both cards, or one card (and also which of the two)


    I think it makes much more sense to have dynamic clocks in Crossfire, because with the extra combined GPU horsepower, you can afford to run slower frequencies. All the while this saves on heat and energy.

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    Re: Crossfire and AMD card owners - query on swapping PCI E priority and Powerplay cl

    Do you mean powertune dynamic clocks? That should still work with crossfire afaik.

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    Re: Crossfire and AMD card owners - query on swapping PCI E priority and Powerplay cl

    Quote Originally Posted by kalniel View Post
    Do you mean powertune dynamic clocks? That should still work with crossfire afaik.
    No I am talking about clocks in the full screen 3d programs. With a single GPU it will fluctuate the core mhz depending on work load requirements. It could be any where from 300 at it's lowest, to it's highest.
    When you have Crossfire enabled, this feature stops.


    In the mean time, I did hear back from AMD and they confirmed that dynamic clocks does not work with Crossfire enabled.
    I had to ask twice just to be clear on their answer. I was sure that it was simply a settings oversight on my part. How can after all this time, that Crossfire does not support dynamic clocking?

    Any ways, query is solved.

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