Mac Pro 3,1 PCI Power Splitter

Discussion in 'Mac Pro' started by honeycombz, Apr 19, 2017 at 1:50 PM.

  1. honeycombz macrumors 6502

    honeycombz

    Joined:
    Jul 6, 2013
    #1
    Hey, I'm planning on installing a GTX 680 into my 3,1. It runs on 2 power cables and I think I've got one of the two power ports in use at the moment and am wondering if it is ok to run both the power cables through a splitter to one of the ports?
     
  2. jeeplj8 macrumors member

    Joined:
    Jan 4, 2014
    #2
    I would guess that depends on what is already drawing juice? Most people report they are fine until they try to run dual cards.

    Oh, and my GTX 970 is dual port, and I am running it off a splitter, but not drawing any other power.
     
  3. honeycombz thread starter macrumors 6502

    honeycombz

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    Jul 6, 2013
    #3
    I'm currently running 1 GPU the 5770 which I would be replacing, the Apricorn Velocity Solo x1, 3 HD spinners and 2 SSDs. That's it. So I definitely wouldn't be running 2 GPUs so do you think I'm fine? Also, can I use any old splitter or is there a specific one I need to get. 6 pin, 8pin... not really sure.
     
  4. TzunamiOSX, Apr 20, 2017 at 12:16 PM
    Last edited: Apr 20, 2017 at 12:21 PM

    TzunamiOSX macrumors regular

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    #4
    Not possible, because the 3,1 has 5 separate 12V rails. The power ports are limited to an absolutely max of around 100 Watt (emergency shutdown), but you need 150 Watt for the 2 ports of the 680.
     
  5. honeycombz thread starter macrumors 6502

    honeycombz

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    Jul 6, 2013
    #5
    Ok, so I need to have one power cable going into one port. I'll see about routing the power to whatever is there in one of the ports already somewhere else as it probably doesn’t need as much as the GPU. Maybe I can split the power off of the optical drive.
     
  6. TzunamiOSX, Apr 20, 2017 at 9:15 PM
    Last edited: Apr 20, 2017 at 9:31 PM

    TzunamiOSX macrumors regular

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    Oct 4, 2009
    Location:
    Germany
    #6
    Maximum of one sata power connector is 4,5 Ampere. A 6-Pin GPU power connector supports up to 6,25 Ampere.

    You need an Y cable for a save gpu use, but there is also the rail problem. Which rail is for what part of the board? Perhaps there is not enough power for a GPU on the drive connectors.

    Why don't use the 680 standing alone? In a 3,1 it is dangerous to get more power than allowed. The 5,1 has a single 12V rail and this gives more options.
     
  7. jeeplj8 macrumors member

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    Jan 4, 2014
    #7
    I ran a 650Ti in my 3.1. Note that it had a single 6 pin power port. I used an 8 pin to 6 pin converter (and an extension because the power port was too far away.)
     
  8. honeycombz thread starter macrumors 6502

    honeycombz

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    Jul 6, 2013
    #8
    Just to doublecheck does anyone know/suggest a comparable GPU that would only require one PCIe slot on the off chance I run into problems? The only other slot I use is for the Apricorn Velocity Solo X1 and I'm concerned if that is not in one of the top 1 or 2 slots I might run into issues. Not positive on that just wanted to doublecheck about GPU alternatives that may be less of a headache.
     
  9. honeycombz thread starter macrumors 6502

    honeycombz

    Joined:
    Jul 6, 2013
    #9
    Just bought an MSI Lightning Nvidia GTX 680 2GB flashed for Mac for a decent price plus 5% ebates and the power cords. Fingers crossed.
     
  10. TzunamiOSX, Apr 21, 2017 at 1:46 PM
    Last edited: Apr 21, 2017 at 1:52 PM

    TzunamiOSX macrumors regular

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    Oct 4, 2009
    Location:
    Germany
    #10
    Every GTX 680 needs 2 6-pin connectors. The 680 OC needs up to 2 8-pin connectors.

    If you need a single slot, single 6-Pin card, use a Quadro 4000 Mac Edition.
     
  11. honeycombz thread starter macrumors 6502

    honeycombz

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    Jul 6, 2013
    #11
    Ok thanks. I'll keep that in mind. Hoping the 680 pans out would way better than the 5770.
     
  12. ActionableMango macrumors 604

    ActionableMango

    Joined:
    Sep 21, 2010
    #12
    I'm confused. What is the splitter for? The 5770 uses one of the two power ports, but you are removing it so you will have both power ports free for the 680.
     

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