OEM ATI 4870 running as x2 lane in x16 slot 1 of 5,1 Mac Pro

Discussion in 'Mac Pro' started by leon771, Aug 10, 2017.

  1. leon771 macrumors regular

    Sep 17, 2011
    I have a 2010 Mac Pro dual processor into which I put a genuine 4870 from my 2009 Mac Pro.

    Today I installed a brand new Inateck KT4004 into slot 4. When I plugged a USB stick into it it took 30+ seconds to mount. I thought this was odd, so opened System Report to have a look.

    When I checked out the PCI section I saw that my ATI 4870 had a link speed of 5.0Gb/s but the bus width was x2, and I presume that it should be x16.

    I didn't have time or the space to try moving the card to slot 2 and seeing what it negotiates.

    Does anyone have any idea what could cause the card to negotiate a lower speed with the GPU?
    Is there anyone running a 4870 in a 2010 Mac Pro? Does it negotiate at x16 or x2?
    According to Apple, the 2010 doesn't "support" the 4870. I'm wondering if the x2 is because the 2010 isn't reading the 4870 properly.

    I've had a few random problems with this machine (shutdowns out of the blue). I've run ASD on it and it comes back pretty "healthy" except for a temp sensor issue on slot 1. I've read on another forum that this is because the 5,1 isn't compatible with the 4870.

    Tomorrow I'm going to swap in a 680 GTX from my 2009 Mac Pro and see if it negotiates x16, to rule out a problem with the backplane board.

    I have an Inateck card in my 2009 that I'm also going to swap into my 2010 to see if the new card is "broken" or whether it also indicates a fault with the 2010.

    Anyone have any thoughts?
  2. h9826790, Aug 10, 2017
    Last edited: Aug 10, 2017

    h9826790 macrumors G4


    Apr 3, 2014
    Hong Kong
    5,1 can work with 4870 properly. And should negotiate at PCIe 2.0 x16. I don't have a native 5,1. But I flashed my 4,1 to 5,1, I consider they are identical on this matter, and that's with the Apple 4870.
  3. leon771 thread starter macrumors regular

    Sep 17, 2011
    I installed my EFI flashed GTX 680 into Slot 1 of the 2010 Mac Pro and it negotiates a x16 lane.
    Install the ATI 4870 and it only negotiate x2 speed.
    I also installed an older KT4004 that I had into the 2010 Mac Pro and it works perfectly, so I don't suspect there is anything to amiss with the PCI slots in this machine.

    I think I was supplied a KT4004 that is underperforming/not within spec.

    Apple is correct in stating that the ATI 4870 isn't compatible with the 2010 Mac Pro. It looks like the SMC isn't able to read temp readings from the card, but it is also unable to negotiable a correct lane width.
    When the ATI 4870 is installed in my 4,1 Mac Pro (flashed to 5,1) it negotiates at x16.
  4. AidenShaw macrumors P6


    Feb 8, 2003
    The Peninsula
    This info popup is on the GPU-Z PCIe info:

    gpu-z.jpg (click to enlarge)
  5. leon771 thread starter macrumors regular

    Sep 17, 2011
    I'm pretty sure that that is not what is occurring here.
    In my 2009 it negotiates x16, but not in the 2010. I think the 2010 just isn't compatible.
  6. itdk92 macrumors 6502


    Nov 14, 2016
    Copenhagen, Denmark
    How can you be sure? It sounds pretty legit.

    Also, if the card is from Apple or flashed properly, it should work just fine.

    It's either Aiden's explaination or a partially faulty card (less probable).
  7. leon771 thread starter macrumors regular

    Sep 17, 2011
    Card is a genuine Apple card.

    If I stick it in my 2009 4,1 then System profiler states x16 width under all conditions of use.
    I should state that my 4,1 has been flashed to 5,1 firmware.

    Remove card and put it into 2010 then it states x2 width. Run Cinebench to get card working and it still states x2 width.

    To rule out any funny software issues I pulled the drive from my 2009 and stuck it into my 2010.
    Still get x2 width only.

    I put my 680 gtx Mac edition into both my 2009 and 2010. Both state x16 width.

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