Saphire 7950 PCIe Lanes

Discussion in 'Mac Pro' started by thedocbwarren, Nov 10, 2017.

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  1. thedocbwarren macrumors newbie

    thedocbwarren

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    #1
    I have a Mac Pro 2010 (5,1) with an EFI Sapphire 7950 (boot screen) running. Everything seems great except I wondered why the system report shows the PCIe lane width as 4x. This machine has 2 16x slots for GPUs. I have it in the so label 16x slot. I have moved this card around to test with no change. I have no idea why this would restrict the bandwidth of the card unless it's a bug.

    Machine running High Sierra.
     
  2. Joe The Dragon macrumors 6502

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  3. thedocbwarren thread starter macrumors newbie

    thedocbwarren

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    #3
    Fair enough, I assume that is the bottom slot hugging the tray? If so I still only get 4x. I had considered trying an nvidia non efi for a speed test on the slot. I like having a full native solution for my pro though vs a web driver.

     
  4. h9826790 macrumors 604

    h9826790

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    #4
    Not ture, both slot 1 and 2 are x16 slots on the Mac Pro 5,1.
     
  5. thedocbwarren thread starter macrumors newbie

    thedocbwarren

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    #5
    I thought so. And to add this is a dual processor 5,1 with two x5690 3.46GHz Xeons.

     
  6. h9826790 macrumors 604

    h9826790

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    #6
    Do you have any picture of your card?

    Most 7950 has dual ROM design, switch to another ROM (most likely no boot screen, doesn't really matter), and then try again.

    If other GPU can negotiate at x16, then obviously it's the GPU's problem, not the Mac Pro.

    Anyway, no need to worry if you really can't fix it. The performance penalty is just about 2.4%, pretty much zero impact on most operation.

    https://forums.macrumors.com/thread...mac-with-2-d700s.1732849/page-5#post-21722712
     
  7. thedocbwarren thread starter macrumors newbie

    thedocbwarren

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    #7
    It’s that real pretty white card. It does have the dual firmware mode for PCs. It’s got s boot screen so it’s set for EFI. I will try another card for gits and shiggles. That said I did notice the geek bench compute is very good and FCPx runs very well so maybe it’s a “who cares.”

     
  8. h9826790 macrumors 604

    h9826790

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    If that's the genuine 7950 Mac Edition card. Then most likely it's damaged. From memory, it's possible that damage some transistor near the PCIe connector during installation / uninstallation, which makes the card can only negotiate at x4 lane.

    If you buy it cheap, and the card is 100% stable, then I will say performance penalty is not a problem at all. But I guess if you pull the card out and examine the card's back carefully, you may able to find out the "why".
     
  9. thedocbwarren thread starter macrumors newbie

    thedocbwarren

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    #9
    --- Post Merged, Nov 10, 2017 ---
    Definitely not cheap and brand new. So curious. I’ll try the nvidia card for fun. I have faster machines I use anyway so it’s more for optimized FCPx usage. The nvidia cards work less optimized for it but well enough.
     
  10. hwojtek macrumors 65816

    hwojtek

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    #10
    I'm not quite sure this is a right direction, but perhaps there is some insight here...?
     
  11. thedocbwarren thread starter macrumors newbie

    thedocbwarren

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    #11
    Interesting. It is listed at 5 GT

     
  12. h9826790 macrumors 604

    h9826790

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    #12
    Wrong direction. The Sapphire HD7950 Mac Edition negotiate at PCIe 2.0 speed natively. No need any transistor mod. Also, that's nothing to do with x4 or x16.
    --- Post Merged, Nov 10, 2017 ---
    In this case, contact the seller. Get a replacement (or refund).

    I don't think both of your cMP's PCIe slot 1 and 2 are broken. Of course, still better to try another card, just make sure something can run at x16. Or put this card in another machine to confirm it is a faulty card.

    And yes, this card has exceptionally good performance in FCPX. But if you don't really need boot screen. And you can run 10.12.6 or higher. I think you better return the card, and get the Sapphire PULSE RX580 8GB card. That's cheaper than a brand new HD7950 Mac Edition card, newer, and much faster in all aspect (including in FCPX).

    It is a 100% OOTB card, but just no boot screen.
     
  13. thedocbwarren thread starter macrumors newbie

    thedocbwarren

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    #13
    Good call. I’ve been tempted to try a new AMD card. The 7950 is exceptional for sure but uses a lot of power and out of date. I use Nvidia GPUs for other purposes with success, however, no denying AMD is a finalcut performer.



     
  14. Michael MP2 macrumors newbie

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    #14
    • Chipset Model: AMD Radeon HD 7950
    • Type: GPU
    • Bus: PCIe
    • Slot: Slot-1
    • PCIe Lane Width: x16
    • VRAM (Total): 3072 MB
    • Vendor: ATI (0x1002)
    • Device ID: 0x679a
    • Revision ID: 0x0000
    • ROM Revision: 113-E2080C-101
    • EFI Driver Version: 01.00.624
     
  15. thedocbwarren thread starter macrumors newbie

    thedocbwarren

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    #15
    That looks right, sadly mine doesn't. I guess it's ok for now but going to troubleshoot a bit more. Mine says 4x lane width.

     
  16. h9826790 macrumors 604

    h9826790

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    #16
    Is there any return window for your card? If yes, don’t diagnosis too long, as long as the cMP can run other card at x16 in the same slot, you better return it. Or at least apply a RMA. As you said, it’s not cheap, and brand new (from OWC???), why you want to pay big money for a may be damaged old card?

    If the issue is just limited to x4 lane. Then not a huge problem at all, in fact, virtually make zero difference than a x16 card on cMP. But the worst part is that we don’t know if there is any other hidden trouble / damage.
     
  17. thedocbwarren thread starter macrumors newbie

    thedocbwarren

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    #17
    Sadly no I never noticed till recently as I was sure I remember it saying 16x at one point before Sierra.

     
  18. h9826790 macrumors 604

    h9826790

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    #18
    Sapphire should provide something like 2 years warranty for a brand new 7950 Mac Edition card. Their CS is actually OK. Quite helpful. May be you can try to open a ticket on their supporting page.
     

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