My (Early 2008) Mac Pro Video Card Question

Discussion in 'Mac Pro' started by boodaddyz, Nov 24, 2013.

  1. boodaddyz macrumors member

    boodaddyz

    Joined:
    Dec 25, 2008
    #1
    Hello,

    I have an early 2008 MacPro with a 980W power supply. I am wanting to get two Radeon 7950's. Can my Mac Pro run two of these cards with the current power supply?

    I currently have the Nvidia 8800 and it only has 1x 6 pin connected to it, but the 7950 requires two 6-pin each. I believe i would need a slitter. Is this correct?

    I appreciate your time, and any advice or help you can offer.

    Thanks!
     
  2. NOTNlCE macrumors 6502a

    NOTNlCE

    Joined:
    Oct 11, 2013
    Location:
    DMV Area
    #2
    The Radeon takes two 6 pin inputs, which exist on the logic board via Mac Pro to 6 pin adapter, and (correct me if I'm wrong) but the most power you can route from the Optical Bay is two Molex. In theory, it should work, converting both Molex to 6 pin, with no Optical Drive. However, this is just what I'm observing, someone more experienced with this should weigh in here.
     
  3. DanielCoffey macrumors 65816

    DanielCoffey

    Joined:
    Nov 15, 2010
    Location:
    Edinburgh, UK
    #4
    You can run ONE 7950 off your internal PSU, not two. If you use splitters you will run a very serious risk of burning out the traces on the logic board if you attempt to run two 7950s off the same two 6-pin power leads.

    You will need to investigate secondary power supplies, either external or in the spare optical drive bay.
     
  4. NOTNlCE macrumors 6502a

    NOTNlCE

    Joined:
    Oct 11, 2013
    Location:
    DMV Area
    #5
    There we go, that corrects my statement. You still may be able to route power from the Optical Drive, but I don't think two molex are going to power a 7950.
     
  5. boodaddyz thread starter macrumors member

    boodaddyz

    Joined:
    Dec 25, 2008
    #6
    Really appreciate the help. Here is my problem. 7950's are very scarce right now, so I ended up getting a R9 280x. I did not see that it required a 6 pin and 8 pin connector. (Thought it was 2x 6 pin)

    It comes with a 4 pin molex to 8 pin adapter. Can I unhook one of the super drives and take the 4 pin molex and connect it to the adapter that the video card comes with? I have extension cables to make it longer. Below is an example of the adapter the video card comes with. Appreciate your help.

    [​IMG]
     
  6. NOTNlCE macrumors 6502a

    NOTNlCE

    Joined:
    Oct 11, 2013
    Location:
    DMV Area
    #7
    I would imagine that would work, that's what I was talking about in my first post. The logic board carries two six pin power adapters, you don't want to run adapters off those, because you will fry your board, like DanielCoffrey said. Give it a shot, I don't know how well the cards work under OS X.
     
  7. DanielCoffey macrumors 65816

    DanielCoffey

    Joined:
    Nov 15, 2010
    Location:
    Edinburgh, UK
    #8
    Can you safely pull 150W off one optical drive molex? That is what will be drawn through the 8-pin connector on the card!
     
  8. ryan42 macrumors 6502

    ryan42

    Joined:
    Dec 3, 2003
    Location:
    Near Houston, TX
    #9
    Oh my god a million times no. There is no reason for that product to exist. You cannot run two power-hungry cards off your Mac Pro's internal PSU. You may be pushing it by attempting to use one. The only converters that are legitimately okay to use take two 6-pin PCIe connectors (rated at 75 watts) and turn them into a single 8-pin PCIe connector (rated at 150 watts). Do not split the 6-pin power connectors. Do not bundle the 6-pin power connectors into an 8-pin and subsequently split the 8-pin. Do not adapt the 6-pin power connector to an 8-pin in a way that makes the card think "sure, I can draw 150 watts from this!" Anything you attempt to do with the optical drive power connectors risks damaging your machine, your card, or both.
     
  9. olliemock macrumors newbie

    Joined:
    Feb 3, 2014
    #10
    Hey,
    so I know this is fairly old but did you have any luck with an R9 280X?
     

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