Question about installing GTX 780 SC

Discussion in 'Mac Pro' started by tripsyou, Apr 20, 2016.

  1. tripsyou macrumors newbie

    tripsyou

    Joined:
    Apr 20, 2016
    #1
    Hello,

    I have a Mid 2010 Mac Pro 5,1. I am about to purchase a GTX 780 SC(http://www.amazon.com/EVGA-GeForce-384-Bit-Graphics-06G-P4-3787-KR/dp/B00K699CRW). It is a regular model and has not been flashed for the Mac. I have read many forums about weather or not this card is compatible and it seems to be, but what I am questioning is how I should have it wired for power. Currently I have a 7970 hooked up with the Mini-PCIe 6 pin to 6 pin and Mini-PCIe 6 pin to 8 pin adapter. Will hooking up the 780 the same way be ok? I have seen that some people use a adapter to pull power from the optical drive sata connections.

    Thanks for any input.
    --- Post Merged, Apr 20, 2016 ---
    I forgot to add that in my Mac Pro I have:

    128GB SSD (OS)
    2TB HDD
    2TB HDD
    3TB HDD
    Radeon 7970 Graphics Card
     
  2. pastrychef macrumors 601

    pastrychef

    Joined:
    Sep 15, 2006
    Location:
    New York City, NY
    #2
    Your current cables should work.

    Later versions of the GTX 780 require Nvidia Web Drivers. The original GTX 780s worked with Apple's built-in drivers.
     
  3. tripsyou, Apr 20, 2016
    Last edited: Apr 20, 2016

    tripsyou thread starter macrumors newbie

    tripsyou

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    Apr 20, 2016
    #3
    --- Post Merged, Apr 20, 2016 ---
    #3
    I've read from a lot of other threads that this card might damage my motherboard due to the power that it pulls. It says that it needs 250 watts. Can it pull that safely from the two mini PCIe ports I'm using safely?

    I have seen that some use a external power supply to run their cards.
     
  4. thornslack macrumors regular

    Joined:
    Nov 16, 2013
    #4
    I used a 780 Classified that req two 8 pin cables and I used two mini-six pin to 8 pin adapters and never had any issues. I even overclocked in Windows for gaming. However, some people have had the power supply trip which immediately turns the Mac off if it draws too much power.

    Generally I think it's pretty safe. People have theorized that you could burn out the pcie power traces but I've never seen or heard evidence of that happening. I'm currently running a Titan X SC (250w) with a six pin and six to eight pin just fine. I did have the computer click off however when I attempted to overclock it so I'm right at the edge of what the expansions pcie cables can provide.
     
  5. tripsyou thread starter macrumors newbie

    tripsyou

    Joined:
    Apr 20, 2016
    #5
    Ok, that is good to hear. I was really not wanting to use a second power supply and drill holes in my MP. I currently have these cables coming from the motherboard. Are you using the same? (just to clarify)

    http://www.amazon.com/Mini-pcie-Mac-pro-Pci-express-6-pin-Cable/dp/B00G2UDJIW

    http://www.amazon.com/JacobsParts-E..._UL160_SR160,160_&refRID=1V5M282GWETQFXXHK9WY
     
  6. h9826790 macrumors 604

    h9826790

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    Hong Kong
    #6
  7. thornslack macrumors regular

    Joined:
    Nov 16, 2013
    #7
    Those look like the right cables for a card that takes a six pin and an eight pin.

    I put an extra power supply in my Mac when I was running 680s SLI and while it's easy enough, it's a lot more power, noise, and heat which I found unappealing.

    The much quoted workaround here if you ever wanted to is to combine both mini six pins into an 8 pin (75w+75w=150w) and combine two sata power ports off the back plane into a six pin (~50w+~50w exceeds the necessary 75w)
     
  8. tripsyou thread starter macrumors newbie

    tripsyou

    Joined:
    Apr 20, 2016
    #8
    I have reached out to him. Can you explain in laymen terms how these cables will share the load compared to the two I'm already using. I'm just trying to understand. Thanks!
     
  9. thornslack macrumors regular

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    Nov 16, 2013
    #9
    It's because it eliminates the 6 to 8 pin. The mini six pin is just a six pin, rated for max 75watts. But the conversion to eight pin means you could be drawing up to 150w through that single port. By combining the two six pins and then redistributing that power, you even the load. So instead of one port pushing a theoretical max of 150w and one port pushing a theoretical max of 75w, they share the total 225w load. Ie each port 112.5w.
     
  10. h9826790 macrumors 604

    h9826790

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    #10
    In your current case.

    mini 6pin (75W, max official power available) -> 6pin (75W, max power draw technically)
    mini 6pin (75W) -> 8pin (150W)

    Obviously the 8pin may cause trouble, in real world test, the mini 6 pin on 5,1 can provide up to ~120W, anything more than that may shut down the Mac (self protection to avoid damage).

    In his case

    2x mini 6pin (75W+75W = 150W) -> bridge -> 6+8 pin (75W+150W = 225W)

    So, each mini 6pin only need to provide up to 112.5W max, just stay inside the real world possible power envelope (still way outside the official limit).
     
  11. tripsyou thread starter macrumors newbie

    tripsyou

    Joined:
    Apr 20, 2016
    #11
    Forgive my ignorance, but if the two mini 6pin are only able to allow 150W(officially available) and the card is pulling 225W due to the 6+8 pin..wouldn't that cause a problem? Since its pulling more than is allowed?

    Also if the computer can only put out 225W and the card(per the specs on the amazon listing) requires 250W, would the card be able to function at 25W less than what is required?

    I know nothing about electrical engineering or anything like that so if I sound like an idiot, its because I'm new to this.
    --- Post Merged, Apr 20, 2016 ---
    Also, would this cable configuration work or would I be better off combining the 2 mini 6 pin to a 8 pin and pulling power from one of the sata ports for the 6 pin connection?

    2X (http://www.ebay.com/itm/MINI-PCI-E-...6276e&pid=100338&rk=15&rkt=18&sd=251529312507)

    1 (http://www.ebay.com/itm/6-Pin-to-8-...530341?hash=item3f2db13ee5:g:Ah0AAOxyrM5THKCt)

    1 (http://www.ebay.com/itm/Black-Sleev...628163?hash=item2107e8f443:g:wxwAAOSwT~9Wh1KT)
     
  12. Obioban macrumors regular

    Joined:
    Oct 19, 2011
    #12
    Is there a place to source a load sharing cable? That sounds like a perfect (if not officially sanctioned) solution for a 250w card! I like that far more than a 6 pin and 8 pin adapter!
     
  13. h9826790 macrumors 604

    h9826790

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    Apr 3, 2014
    Location:
    Hong Kong
    #13
    Possible, as you said, t's outside the official limit, however, so far, no cMP user here report that the Mac Pro was killed by pulling too much from the mini 6pin port. I driver 2x 7950 from those mini 6pins only, no problem at all. The only time I able to shut down the cMP (by drawing too much) is when I OC both cards under windows for gaming. I personally won't recommend anyone to do it, and I know what I am doing, I am willing to take the risk. If those mini 6pin has enough power to drive 2x peace heater, then drive a 780 SC with proper load sharing should not be a problem at all.

    No, the mini 6pin is rated up to 75W, but not only able to provide 75W, if the card pull more, it will deliver more, that's the problem why we worry about the card pulling too much. If the mini 6pin can only deliver 75W regardless the card's demand, then there is nothing to worry about. Anyway, AFAIK, if only 25W under the TDP, the card should able to function normally, the worst is just the card's performance may be a bit lower.

    2x mini 6pin -> 8pin is a better way to power the card.

    However, SATA to 6pin is NOT a good idea. 2x SATA -> 6pin is much much better. IMO, possible kill the mini 6pin is not a good idea, but obviously there is a protection at there, and a Pixlas mod can easily be the work around if I really kill the mini 6pin port. However, so far, no actual report about how much power the SATA port can deliver on the 5,1, and what will happen if pulling too much from the SATA port. And I don't want to kill an I/O port as well.

    Anyway, to sum up, by pulling too much, you may permanently kill your Mac Pro. That's the worst case (other than catch fire etc), IMO, the chance is very very low (if you do the load sharing correctly), but you must understand what you are doing. A single 6->8 or a single SATA to 6, IMO, is not a good idea. That's the greatest risk configuration.
     
  14. tripsyou thread starter macrumors newbie

    tripsyou

    Joined:
    Apr 20, 2016
    #14
    Ok, thank you so much for clearing that up.

    The card only has a 6 and 8 port for power. So using these two cables would be the best way to go about powering it? I do not plan to overclock this card.

    http://www.amazon.com/JacobsParts-E...4035&sr=1-2&keywords=mini+6+pin+to+8+pin+pcie

    http://www.amazon.com/Mini-pcie-Mac...4025&sr=1-1&keywords=mini+6+pin+to+6+pin+pcie
    --- Post Merged, Apr 20, 2016 ---
    OR would it be better to use this setup. I am trying to copy the cable configuration from (http://forums.macrumors.com/threads/gigabyte-hd7950-rom-observations-power-draw.1966954/)

    2X (http://www.amazon.com/Mini-pcie-Mac...4025&sr=1-1&keywords=mini+6+pin+to+6+pin+pcie)

    1 (http://www.amazon.com/Silverstone-S...461184824&sr=1-1&keywords=6+pin+to+6+pin+pcie)

    1(http://www.amazon.com/JacobsParts-6...461184861&sr=1-2&keywords=6+pin+to+8+pin+pcie)
     
  15. h9826790 macrumors 604

    h9826790

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    Hong Kong
    #15
    What's the difference? it looks like both options are the same, each mini 6pin works separately.

    The cable in that thread should be a custom cable, which make both mini 6pin in parallel, and share the load.
     
  16. tripsyou thread starter macrumors newbie

    tripsyou

    Joined:
    Apr 20, 2016
    #16
    Ok, I missed that the cable was custom.

    I guess my only option is to power the cable with a mini6 to 6 and a mini6 to 8. I'm not sure where to get that kind of custom cable or know how to make it.

    Thanks!
     
  17. thornslack macrumors regular

    Joined:
    Nov 16, 2013
    #17
    Just do that, you'll be fine.

    All of the information above is accurate and good advice, but is generally perhaps over cautious or geared to users who's mac is on the bleeding edge of max power due upgrades, other internal pcie devices, tons of HDs, peripherals etc. My cMP has two upgraded 130w processors and a bunch of other stuff under the hood and an over powered GPU and knock on wood everything works fine using a mini-six to eight pin. Keep in mind the pcie slot itself supplies 75w so your card will be properly powered.
     
  18. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #18
    2x mini 6pin -> single 8pin -> 6+8 Pin

    Use the single 8pin as bridge. Just make sure one cable have male 8pin, the other one is female.

    http://www.moddiy.com/products/Appl...tandard-PCI%2dE-8%2dPin-Video-Card-Cable.html

    http://www.moddiy.com/products/Bitcoin-Mining-PCI%2dE-8pin-TO-2-PCI%2dE-6%2b2pin-Splitter-Cable.html
     
  19. Obioban macrumors regular

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    Oct 19, 2011
    #19
  20. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #20
    That's a 6+2 plug, you can use it on 6pin or 8pin, no need to get another cable.
     

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