Running dual 4870's in a 2009 Mac Pro

Discussion in 'Mac Pro' started by VirtualRain, Mar 10, 2009.

  1. VirtualRain macrumors 603

    VirtualRain

    Joined:
    Aug 1, 2008
    Location:
    Vancouver, BC
    #1
    Based on what WonderSausage has shown us, it looks like a factory installed 4870 utilizes dual 6-pin PCIe power cables that connect to something on the motherboard (presumably dual 6 pin connectors).

    On my old SLI PC gaming rig, I used a pair of PCIe 6-pin "Y" cables to serve two cards (both with dual power connectors) from one pair of PSU PCIe power cables.

    Here's the product I used:
    http://www.performance-pcs.com/catalog/index.php?main_page=product_info&cPath=186&products_id=2664

    I'm guessing, you could easily use this to add a second PCIe powered 4870.

    Those concerned about over loading the MP's power supply may have a valid argument but only if both those graphics cards were rendering 3D to the max while the CPU's were also simultaneously maxed. A very unlikely event even if gaming under Windows with Crossfire (since few games can saturate all that CPU). I can't imagine any circumstance under OSX where both CPU's and Graphics cards could be at max power draw. Certainly, single CPU systems would have enough power supply overhead to get away with this.

    The benefits of this would be the potential for Crossfire gaming in Windows and also huge OpenCL capabilities under OSX.

    Just a thought.
     
  2. Setmose macrumors regular

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    Nov 7, 2007
    Location:
    Jerusalem, Israel
    #2
    Not sure how the power stats add up, but new Mac Pro is good to go with 4 Nvidia cards -- that is a CTO option straight from Apple. :apple:
     
  3. macz1 macrumors 6502

    macz1

    Joined:
    Oct 28, 2007
    #3
    The power draw of two HD 4870 should be supported by the Mac Pro's power supply unit (almost a kW IIRC). The only issue I see is the eventual lack of cables in order to connect both cards. 4 auxiliary connectors are needed while there are only two plus the ones of the optical drives...
    As the optical drives do not draw much power however, using their power connectors for the cards (and putting an Y-splitter to power the optcal drive) should work well.
     
  4. mackmack macrumors member

    Joined:
    Mar 3, 2009
    #4
    While it's a 1000 watt power supply, there may be issues depending on whether or not the 12V rail the connectors are on can supply enough current to serve the cards.

    Nowadays you see single 12V rail power supplies that deviate from ATX spec with massive 48+ amp 12V rails to reduce compatibility problems. Not sure this is the case with the mac pro psu.
     
  5. VirtualRain thread starter macrumors 603

    VirtualRain

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    Location:
    Vancouver, BC
    #5
    I guess you didn't read my post... There is a simple solution to the power connection problem.

    Others, how accessible is the power supply in the Mac Pro to see if there are specs printed on the actual unit?
     
  6. KBS756 macrumors 6502a

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    Jan 27, 2009
    #6
    id like to see someone try this how soon are the radeons shippin from apple?
     
  7. shokunin macrumors regular

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    Jun 7, 2005
    #7
    What would worry me, is that the 6pin connectors are on the motherboard. If you exceed whatever rated amperage the motherboard was designed to provide, you can easily fry the motherboard.

    If these connectors were connected directly to the PSU, I'd be more comfortable using a cable splitter to provide enough juice to both cards.
     
  8. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #8
    All HD4870 cards use 2x pin PCIe power connectors.

    I'd be careful with using Y cables though, as the board's traces may not be able to handle that much power. :eek: I've no idea ATM of how the rails are shared (what resources on what rail) for the PSU, but it should be able to supply the power if you can get to it. ;)
     
  9. macz1 macrumors 6502

    macz1

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    #9
     
  10. VirtualRain thread starter macrumors 603

    VirtualRain

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    Vancouver, BC
    #10
     
  11. frimple macrumors 6502

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    Nov 18, 2008
    Location:
    Denver, CO
    #11
    Maybe I'm missing something here, but what would be the benefit of this versus installing a 4870x2?
     
  12. MacVidCards Suspended

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    Hollywood, CA
  13. KBS756 macrumors 6502a

    Joined:
    Jan 27, 2009
    #13
    lol prob useless because this comes from someone in apple chat (the sales dpt on their site)

    do u know if a mac pro can run
    dual radeon 4870 hd's
    ?
    One moment while I research that for you.
    kk
    No problem.
    i can use 2 radeons or ur still lookin
    ?
    Yes, you can.
    I apologize. I read your question incorrectly at first.

    ur sure this is possible without overexerting power and causing damage to the system?
    http://store.apple.com/us/product/MB999ZM/A
    2 of these
    one ordered with the system and one ordered seperately
    Just one moment.
    k
    Thank you.
    Yes, the Mac Pro will allow you to use 2 ATI Radeon HD 4870 graphics cards.


    bold is the guy lol dk how much he knows but he took 10 mins before replyin (lol prob not all that credible but just wanted to see what they had been told)
     
  14. VirtualRain thread starter macrumors 603

    VirtualRain

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    #14
    I can't imagine the formal position on this is that it's supported given the power connectors they provided. If the formally supported dual 4870's they would have provided the power connections for two.
     
  15. xparaparafreakx macrumors 65816

    Joined:
    Jul 29, 2005
    #15
    This is what I would do. I posted this before assuming they were still going to give us 2 6-Pin PCIe.


    Then I thought about it and is there still Molex up there on the optical drive? Last I looked, it was SATA power and I do not know if you can convert SATA power to PCIe 6-Pin.

    If I were to do it, I would use one of these to help me. Put one in an optical drive slot and dont worry about *ucking with the power supply.
     

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  16. gelid macrumors member

    Joined:
    Dec 17, 2008
    #16
    That's one way to do it I guess, but that will be a lot a cabling to run to/from the drive bay (there may not be enough space in the case to run all those cables). You would need to run AC power to the drive bay to power this, then run the 6-pin PCIe power back down to the PCIe slots.
     
  17. KBS756 macrumors 6502a

    Joined:
    Jan 27, 2009
    #17
    anyone know when one of us will be able to get their hands on 2 of these so we can actually test this?
     
  18. xparaparafreakx macrumors 65816

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    Jul 29, 2005
  19. xsoniccrackersx macrumors newbie

    xsoniccrackersx

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    Location:
    San Francisco
    #19
    Yeah I am going to put a Radeon 4870x2 HD along with the Radeon HD 4870 in crossfire for gaming for BootCamp and just use the Single 4870 for Mac OS X when I get my new Mac Pro. To achieve this I'm going to purchase an external power supply and route the cables through the last open PCI slot grate to play it safe. Ganna also use a KVM Switch to switch between cards with monitors. Will see how it turns out.

    EDIT:

    Seems like KBS756's Rep was also correct.
    I just spoke to 2 representatives from apple about this and they both stated this can be done without the use of a external power supply with no problems and that they helped users with this same configuration with success.

    Jason T: The PCI Express slots offer 300W combined maximum for all PCI Express slots
    You: I see.
    Jason T: It does state in this rumor site thread that the individual thought that it may have a potential to experience power issue if both cards were at maximum uses while the processor was overclocked simultaneously
    I have sold this configuration before selling one card configured and one separately
    You: I just wanted to know whether I should play it safe and purchase an external power supply to supply the other graphics card and route the cables through the remaining PCI slot grate.
    Jason T: And to address your concern...
    Jason T: All slots provide mechanical support for 16-lane cards
    Jason T: I don't see any reason why you would need to

    Seems promising. I will test it with caution and have a power supply just incase.
     
  20. d525125 macrumors newbie

    Joined:
    Mar 14, 2009
    #20
    Will follow this thread because I'm interested in running dual 4870's for Crysis, Far Cry 2, etc., but have never dealt with Crossfire at all. Can anyone point me to a "Crossfire for Dummies" link or equivalent that will get a newb competent on issues like power connections, how to insure choice of 2nd card both works and doesn't introduce problems in OS X, etc.

    Also, anybody know if it will be possible to use Mac 4870 for OS X and GTX295 for Windows in new Mac Pro, and what steps it would require? If it will work, is that preferable to dual 4870 Crossfire? Pros and cons?

    Thank you for any help - have been searching a lot of threads here and at AppleInsider, info is scattered all over the place, hard for newb to synthesize.
     
  21. jmpage2 macrumors 68030

    jmpage2

    Joined:
    Sep 14, 2007
    #21
    You won't be able to run Crossfire in OS X because the operating system isn't going to support it.

    It's questionable right now that you would be able to even have two 4870s in there at all, let alone run them in Crossfire mode.

    Assuming that the physical hardware in the Mac Pro could handle a cross fire configuration you would have to shut down and then manually set it up for Crossfire with the additional cables, etc, and then boot it up into Windows to do Crossfire gaming.

    I honestly don't see OS X supporting Crossfire configurations any time soon, since Apple seems to have very little interest in providing high end gaming solutions with their computers at this time.

    Also, final point, games have to be written to take advantage of Crossfire capabilities, and most aren't.

    If you want to see a review of a 4870 Crossfire setup, including benchmarks, you can look here;

    http://www.legitreviews.com/article/734/11/
     
  22. gelid macrumors member

    Joined:
    Dec 17, 2008
    #22
    Correct.

    It is a matter of power contraints, particularly the lack of enough connectors for the four PCIe power connector that would be needed for two 4870s. Also, it remains to be seen if the power supply is beefy enough for ttwo 4870s.

    You can leave the crossfire cables connected when in OS X. It's not going to hurt anything, but only one card will be used in OS X Leopard.

    Agree. It would be a nice surprise if it was included with Snow Leopard, but I'm not counting on it.

    Sort of. There are ways for forcing games to use Crossfire, even if they don't officially support it, but doing so can actually make some games run slower.
     
  23. matthew.russo macrumors regular

    matthew.russo

    Joined:
    Mar 20, 2009
    Location:
    Australia
    #23
    I was thinking of doing a similar setup. The theory is the Single Apple card would still work under OSX and the two cards with a crossfire setup in Windows Vista (32bit)

    The setup would be an Apple ATI HD4870 and a PC ATI HD4870.

    Both cards run the same spec @ 512mb GDDR5.

    How well is Crossfire is supported on the Mac Pro 2008 with the ATI 4000 series, there are 2 x 16 PCI-E slots available.
    Are they any other requirements for Crossfire? ie. is a cable required to link the cards? If so does the apple card have the port available?

    The other requirement which is obvious is power. The 4870 requires 2x 6 pin power connectors so a second PSU is required. The one mentioned above in this thread would be ok..but can you connect it through the mac pro mb power cable? Is it the same as a PC power connector?

    Any help or ideas would be muchly appreciated. Does this sound plausible? Has anyone tried crossfire in the mac pro?
     
  24. AGDenton macrumors newbie

    Joined:
    Feb 19, 2008
    #24
    Every PC 4870 card I've seen comes with a Crossfire bridge, which you'll need to link the two the two cards together... Conveniently, there's just enough room above the Mac Pro's memory riser block to fit one. Once you do that, Crossfire is just one checkbox away in Windows, and works as expected.

    Be aware, however, that I got a kernel panic/ blue screen in OS X every time I've booted into OS X with two cards so far. This is a video driver bug that will hopefully get fixed by 10.5.7... In the meantime, I have to unplug one of the cards when I boot OSX.

    Either that, or use two Y splitters.
     
  25. matthew.russo macrumors regular

    matthew.russo

    Joined:
    Mar 20, 2009
    Location:
    Australia
    #25
    Thanks for the useful info. I'm a little worried about using y splitters as it may draw to much power at peak, each card can pull up to 300w.

    Would you not get the kernal panic if it was an apple card, or a flashed 4870 (not sure if they can be done yet)?

    Cheers,
    Russo
     

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