Adding a second PSU with pics!

Discussion in 'Mac Pro' started by Macinsquatch, Apr 13, 2015.

  1. Macinsquatch, Apr 13, 2015
    Last edited: Apr 14, 2015

    Macinsquatch macrumors member

    Joined:
    Mar 28, 2015
    #1
    Hello my fellow Apple enthusiasts, I figure I will take you on my little adventure of adding a second PSU to my 09 mac pro so that I can power dual GPUs. I will caution anyone who wants to follow in my shoes to do this in a sound proof area with no children around as the cursing may scar them.

    First off a little about this machine. I was running a 08 Mac Pro that was running out of upgrade options, was cooking ram at regular intervals and in general slower than what I wanted. So I sold it, and found a nice 2009 Mac Pro on Ebay with a 7950 in it and dual 2.26 quads in it.

    So I ordered a GTX 970, a set of de-lidded X5690's, and a used Visiontek Juicebox and proceeded to install everything. Now as everyone who has opened one of these up knows, there is little room to add things that Apple didn't intend to be there. Silly Apple...

    So at first I just ran the cables around the cross bar of the case and left the side off, running the power cord out of the dvd slot in front, like a neanderthal.

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    But we are a civilized society so I figured cables should be run inside the case and proceeded to order a custom set of PCI cables from the internet where they don't speak english. I asked for 2 6 pin PCIe cables 24" long. I received a single 8 pin to dual 6 pin cable 24" long.

    Okay, well the Juicebox has two 8-pin and two 6-pin plugs so this should work. Let the surgery begin!

    First things first, I need to remove the pins from the 6 pin connector (luckily they left one of the 6 pin connectors off). So I made some tools.

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    Rudimentary as they may be, they did work. So lets start running some cables!

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    Beautiful, cables routed with no cutting of the case! Now lets run the power.

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    That won't fit through the small cable route.

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    Alright, end of the power cable removed and routed through the same spot as the PCI cables. The observant of you will notice the error of my ways though...

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    Measure twice cut thrice! That power cable won't fit through the empty PCI slot! So I get to pull the cable and run it up the case again, as is life.

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    Alright, everything routed...backplate reinstalled....lets power this beast up.

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    And click.....nothing

    Try as I might, cursing at it didn't fix the issue. In fact something was very wrong, power button did absolutely nothing. Unplugging the power and trying again resulted in the same thing, a single click and then nada.

    Turns out the little power supply cannot handle the 8-pin power being split, damn custom cable. Anyone who has seen the cables that come with the Juicebox knows they are beasts. After having waited 2 weeks to get these cables I was out of patience.

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    That is one of the two cables pushed through the small area precut for cables. Still no case mods. But the second cable wasn't going to fit without a fight.

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    I thought I had won't the battle...

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    At this point I have gone into a slight fit of rage, not only did I have no parts but my tools for this entire venture were these:

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    A pair of pliers I found on the side of the road (literally), my extraction tool and a small flat head screwdriver. Clearly prepared, I did what any man would do.

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    I CAREFULLY disassembled a pin from my custom cable. It was useful after all. Then installed it on the wire with the broken pin and was back in business.

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    Almost finished, the cables wouldn't reach with the back plate in so I ended up having to leave it out, plus I couldn't slide the DVD tray in all the way due to the HUGE ferrite cores on each cable, plus the massive girth of the cables themselves.

    Fired it up and all is well, no case mods and I even managed to use the cables provided with the aux PSU. Both Dell P2715Q 4K displays are humming away at 60Hz. Hope you all enjoyed my little adventure.
     
  2. lewnworxx macrumors member

    Joined:
    Mar 19, 2015
    #2
    Well if all you wanted to do was run a pair of GTX970's, you could have got pair of splitter cables and ran them off the 6 pins. Several of us are, no mods required.

    They stay well under the 75W per 6 pin limit. Now if you want to run Titans or 980's or AMD's that's another story. I went 970's just to avoid what you went through.

    Nice job documenting the process.
     
  3. Macinsquatch thread starter macrumors member

    Joined:
    Mar 28, 2015
    #3
    Oh I know, but since this machine came with a Sapphire 7950 Mac edition I figured I might as well use it. The bonus is that if I want to add something like a 980 or titan I have the power for it. Plus the boot screen really helps for OS and driver updates.

    Really the result that is interesting is that you don't need cutting of the case or special cables to install one of these. Just a little determination.
     
  4. lewnworxx macrumors member

    Joined:
    Mar 19, 2015
    #4
    True enough. My "fix" for the non EFI 970's is having a GT120 in slot 4 that is what feeds the 2 1920x1200 monitors. The 970's are not even used for video, just GPU compute. Granted the GT120 is a slow ass card, but it is EFI so I have boot screens, and I don't game so it's fine for CAD work and playing back QT files of the output animations.

    I'd considered going with a Titan or 980, but I could get a pair of the 970's for just a scosh more than a 980 and well under that a Titan X would run, and the pair render faster than either the a single 980 or Titan X.
     
  5. Macinsquatch thread starter macrumors member

    Joined:
    Mar 28, 2015
    #5
    The last thing to do is free up that last PCI slot that the power cable is running through and solder the Aux PSU power into the leads of the Mac Pro PSU. But one step at a time for this beast.
     

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