PCIE limitations in windows and mac? Or just mac?

Discussion in 'Mac Pro' started by mazuma, May 8, 2012.

  1. mazuma macrumors member

    Joined:
    Mar 28, 2005
    #1
    Ok, so I'm still trying to gather information before I decide which video card to get. Cost is a large part of the equation. I can't really justify throwing $500 dollars at a video card right now. I would love to, but can't. But, I also want to make sure I don't miss getting better performance if I spend just a bit more.

    1. MacVidCards has cards that will run full PCIE 2.0 with boot screen. Do stock cards run at 2.0 or 1.0 when in windows (bootcamp)? Is the limitation strictly on the mac side, or both?

    2. Looking at maybe getting a Nvidia GTX 560 TI. Do I need the second cable to install like you do for the 570? Couldn't find any info on this.

    Thanks in advance.
     
  2. MacVidCards Suspended

    Joined:
    Nov 17, 2008
    Location:
    Hollywood, CA
    #2
    I am about 90% certain that the PCIE 1.0 limit was imposed by Apple to keep flashed cards one step below "The Real Thing"

    It applies to all flashed ATI/AMD cards since 4870. Dig deep and you will find posts by "Beige" a writer for Ars who posted here about this issue with a 1GB 4870 when those were new, he switched back to an Apple 512 Meg model to run Mudbox, said 2.5 was killing it for him.

    http://forums.macrumors.com/showpost.php?p=7485539&postcount=933

    If you read all of his posts, it was wrecking the experience for him to the point that he sold his flashed 1Gb 4870 and went back to Apple 512 Meg model.

    "any leads on the 5.0 GT/s speed? I'm going to sell this 1 GB Sapphire when 10.5.7 comes out next week since the Apple 512 MB 4870 is a bit faster with the faster link speed (generally UI responsiveness and Mudbox)."

    All flashed or PC BIOS 4870, 5770, 5870, 6870, and 6950/70 cards have this issue.

    Flashed 8800GTs and GTX285s are fine at 5.0, but non flashed GTX4xx and GTX5xx cards running "Magic Drivers" or ATY_Init all show same issue.

    The limit is read by the EFI and enforced in Windows as well as OSX. Anyone with one of the affected cards can verify in Windows using GPU-Z. Card will stay at 1.0 PCIE if you run the "Stress Test" or even "Furmark". No amount of stress will kick it into high speed mode.

    For many uses the difference will be negligible. Beige found places where it was a problem. YMMV.

    From the posted tests, this issue is especially important if you run a card in a 4x or 8x slot.

    We are the ONLY group selling flashed cards that run at full speed. The other Ebay guys are selling cards you could flash at home with 15 minutes of effort and get same partially working result.
     
  3. CaptainChunk macrumors 68020

    CaptainChunk

    Joined:
    Apr 16, 2008
    Location:
    Phoenix, AZ
    #3
    1. I could be wrong, but I would think that when a stock PC (BIOS, non-flashed) card is booted into Windows via Bootcamp, it should behave exactly like the card would if it were booted in an actual PC running Windows. Hence, no PCIe speed limitations while in Windows. But on the Mac OS X side, you'd throttled down to to PCIe 1.0. But, the real world advantages of PCIe 1.0 vs. 2.0 are dependent on application.

    2. The 560 Ti requires two 6-pin power cables, just like the 570 does. Straight from NVIDIA's spec sheet, actually.
     
  4. MacVidCards Suspended

    Joined:
    Nov 17, 2008
    Location:
    Hollywood, CA
    #4
    You would be right in a "fair" world, but EFI sets this so it DOES affect Windows. You are welcome to borrow some cards and verify. Or just go to Best Buy or Fry's and pick up a GTX570 and try it at home in Bootcamp. Then bring it to me and try again. All stock PC cards will run at PCIE 1.0 in a Mac Pro in any OS you boot.
     
  5. CaptainChunk macrumors 68020

    CaptainChunk

    Joined:
    Apr 16, 2008
    Location:
    Phoenix, AZ
    #5
    Oh, I believe you. ;)

    I just wasn't sure whether that was a limitation imposed by the EFI boot ROM in the Mac itself or not.
     
  6. mazuma thread starter macrumors member

    Joined:
    Mar 28, 2005
    #6
    Thanks for the replies and the info. This is fairly confusing stuff for the average layperson. More to think about and a decision to make soon! Thanks again.
     
  7. redarc macrumors member

    Joined:
    Sep 6, 2011
    #7
    yeh

    you can be sure of this.. i'm suing an 6970... and in window side.. ti run at 1.0... so it really suck comparised to 5870.... i removed card... i'll use in the new windows machine i bought.. got bored of all this s... limitation of mac os x...
     
  8. CaptainChunk macrumors 68020

    CaptainChunk

    Joined:
    Apr 16, 2008
    Location:
    Phoenix, AZ
    #8
    Well, a lot of us begrudgingly deal with it. It's the price you pay for wanting to run better GPUs in OS X. :p
     

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