Can a early-2009 Mac Pro use two ATi 4870 video cards in parallel?

Discussion in 'Mac Pro' started by thermodynamic, Sep 28, 2009.

  1. thermodynamic Suspended

    thermodynamic

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    #1
    Like "Crossfire" or some Mac equivalent, so anything using OpenGL and OpenCL would truly fly?

    I did a little research and found nothing; maybe it was a bad use of keyword choices, so I thought I would ask for somebody who's had experience here.

    Thank you kindly!
     
  2. thermodynamic thread starter Suspended

    thermodynamic

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    #2
  3. TheStrudel macrumors 65816

    TheStrudel

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    #3
    Actually, two cards can be run. Some forum members have done it. Also, that 300w maximum refers to what is provided by the PCI-express slots (not power taps). Your Mac Pro's power supply can deliver a kilowatt of juice. People here have either used a spare molex connector from the optical drive bay (in 08 Mac Pros) or by using a Y-splitter on the PCIe power tap on the logic board.

    However, a search of 's website would have shown you that it's putting the cart before the horse.

    There's no mention of SLI or Crossfire anywhere on 's website, nor any mention of using more than one GPU for anything but display output. There is no support in OS X at this time for using more than one GPU simultaneously for anything other than display output.

    The reason people have two GT120s is not for "putting them in parallel" but to have four different display outputs or the ports you need.

    Realistically, having more GPUs is not much more helpful than having more CPUs: software needs to be coded to take advantage of it. And that's only just been implemented in Snow Leopard, so now people need to write the apps.
     
  4. thermodynamic thread starter Suspended

    thermodynamic

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    #4
    Cool, thx for the info and clarifications!
     
  5. lannister80 macrumors 6502

    lannister80

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    #5
    FYI: If you use two flashed 4870s, you can use them in crossfire mode in Windows via Bootcamp.

    If you get two Apple OEM 4870s, they DO NOT WORK in crossfire mode in Windows. Something in the hardware prevents them from doing so.
     
  6. Pressure macrumors 68040

    Pressure

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    #6
    You got it wrong. The logic board is rated at supplying 300 Watts of power because it has 4 PCI-Express slots that each supply 75 Watt (4 x 75 Watt = 300 Watt).

    The power supply in itself is 980 Watt and is capable of supplying more than enough power for two Radeon HD 4870.
     
  7. thermodynamic thread starter Suspended

    thermodynamic

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    #7
    I don't do Windows. :D

    I suspect it's the Intel chipset. When I was a PC-lover (Asus P5Q Deluxe), it supported Crossfire but not SLI. I was told it's something in the chipset that accommodates one or the other video platform. I don't do heavy gaming to begin with, and I was thinking more of OpenCL than anything else... :)
     
  8. 300D macrumors 65816

    300D

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    #8
    SLI and Crossfire are not (currently) possible in OSX.
     
  9. TheStrudel macrumors 65816

    TheStrudel

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    #9
    Actually,  crippled their OEM 4870 to preclude crossfire. But Crossfire is motherboard-agnostic. It doesn't care, it just needs the interconnects. SLI requires motherboard or software support of some sort or a combination of the two, I can't remember which. Netkas could tell you more.
     

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