Mac Pro 5.1 and two Radeon 5770

Discussion in 'Mac Pro' started by Justin Bailey, Apr 20, 2018.

  1. Justin Bailey macrumors newbie

    Aug 1, 2014

    I bought second ATI Radeon 5770 GPU for my MP today. Problem is that I can't get both of them running at the same time.

    GPU I bought today is non-Apple GPU but another 5770 is original GPU for MP.

    Both of them works just fine when I use just one of them but if I try to use both of them at the same time, then monitor that is connected to non-Apple GPU doesn't show a picture. I can see that monitor in settings though but screen stays black. In settings non-Apple GPU is shown as "ATY,Hoolock, 1024 Mb" when both GPUs are installed but when I use just that "non-Apple GPU" it is shown as 'ATI Radeon HD 5000, 1024 Mt'

    Computer is Mac Pro 5.1 and OS is macOS 11.13.4. I use PCIe slots 1&2 for GPUs.

    Anyone knows what is the problem and how could I fix it? Or is it even possible to fix?
  2. h9826790, Apr 20, 2018
    Last edited: Apr 21, 2018

    h9826790 macrumors G4


    Apr 3, 2014
    Hong Kong
    Try another port.

    There is nothing you can do. Whenever, you boot a non Apple (PC) card with a Apple card. The Mac EFI on the Apple card will also apply on the PC Card. Therefore, if your PC Card is not a reference card, some port(s) has very high chance that will be disabled.

    Some possible solutions are

    1) use the remainly work port (hopefully there is any)

    2) flash your Apple card with the PC ROM. So that no more Mac EFI, no more boot screen, but the macOS will fall back to use the generic Radeon framebuffer for both cards, and all ports should work. (NOT recommend in general, if you willing to give up boot screen, there are plenty of options)

    3) sell the PC Card and get another one, and buy the reference model this time.
  3. Justin Bailey thread starter macrumors newbie

    Aug 1, 2014
    Darn. That's what I thought. I tried with different slots as well but it didn't work. Maybe I just buy one good - or at least better GPU. That card was just so cheap so I had to buy it and test it.

    Thanks anyway.
  4. MIKX macrumors 6502a


    Dec 16, 2004

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