[Mac Pro 4,1] How does one power a non-Sapphire 6+8 Radeon 7950?

Discussion in 'Mac Pro' started by tibbsy, Apr 1, 2015.

  1. tibbsy, Apr 1, 2015
    Last edited: Apr 1, 2015

    tibbsy macrumors newbie

    Joined:
    Apr 1, 2015
    #1
    Hello all,

    I've searched the forum for keywords such as 7950, power requirements, etc. but wasn't able to find a definitive answer on this. I think there seems to be debate, primarily around anecdotal experience vs. system recommendation. I digress.

    I recently picked up a second-hand Mac Pro. I believe it's a 4,1 with the following hardware:

    • 2.66 Ghz Quad-Core Intel Xeon
    • 12GB DDR3 RAM
    • 640GB HDD
    • GeForce GT 120 512MB

    My current plan is to add an SSD and replace the video card; it's that latter upgrade I have a question about. I have an opportunity to buy one of two 7950 models for $100 a piece: a Gigabyte Windforce 7950 3GB or a MSI Twin Frozr 7950 3GB. Both very comparable, well-performing, albeit non-Sapphire Mac 7950s. And both just a fraction of what a Mac Sapphire 7950 would cost me. I was looking at this image of the Gigabyte board and this image of the MSI board, both courtesy of Newegg, and saw that they have 2 6-pin connectors. Great, no problem based on what I read in the forums - flash and go!

    But the seller for the boards confirmed for me that both cards actually have 6+8 pin connectors. And I'm reading conflicting information about what I should do. My ultimate question is 'can I buy one of those boards, install it into the Mac Pro 4,1 and have it work?' but to answer that it sounds like there are two sub-questions:

    • can I use molex connectors to convert a 6-pin to an 8-pin connector for this, or can I just plug in two 6-pin connectors?
    • some users recommend an "auxiliary power supply" - what does this entail and how is it different from just replacing the PSU?

    Any links to appropriate threads, tutorials and the like are much appreciated. Thanks in advance!
     
  2. AndreeOnline macrumors 6502

    AndreeOnline

    Joined:
    Aug 15, 2014
    Location:
    Zürich
    #2
    The MSI R9 280X 3GB runs in my Mac Pro 5.1 with a 6+6to8 adapter.

    I'm using both 6 pin PCIe booster cables to power this card.

    I have had no issues running FCPX, Resolve or game benchmarks.
     

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