980Ti, internal power?

Discussion in 'Mac Pro' started by AkuskaUK, Nov 8, 2016.

  1. AkuskaUK macrumors 6502

    AkuskaUK

    Joined:
    Mar 18, 2011
    Location:
    Shanklin, Isle Of Wight
    #1
    Hi everyone,

    I recently purchased a 980Ti to replace my ageing 770, on MVC's website they say that their flashed versions are able to ran on internal power. I rang MacStoreUK (MVC's Europe supplier) and they said that it should be ok once flashed too.

    The questions I have are:
    1. How will the card be fully powered if there is an 8 pin connection when the Mac Pro have 2x6?
    2. Will a 6 pin be ok in there or will I have to get a 6 to 8 converter?
    3. Will that be safe using said converter?
    4. Is there a better way to power the card that I don't have to run an external PSU?
    5. Would I be able to use the optical drive Sata connection for more power?
    6. Will I have to remove any drives so that I'm not overloading the PSU?
    If these questions have already been answered, I apologise.
    Thanks in advance!
     
  2. orph macrumors 65816

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    UK
    #2
  3. Synchro3 macrumors 68000

    Synchro3

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    Jan 12, 2014
    #3
    1. With a 6 to 8 pin and a 6 to 6 pin cable. Already included with the card when buying from MVC.
    3. Yes
    4. No need for an external PSU at all if you don't overclock the card
     
  4. superparati macrumors member

    superparati

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    Apr 11, 2016
    Location:
    London
    #4
    Hi,

    I've this version eVGA 06G-P4-4995-KR (from amazon) which has one 8 and 6pins.
    I'm powering the card using the 2x6pin to 8pin of the card and the other I get the additional 6pin from the optical bay where I have also a SSD.
    Everything seems to work like a charm without issue on macOS and Window.
     
  5. AkuskaUK thread starter macrumors 6502

    AkuskaUK

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    #5
    Won't the 6-8 draw too much power from the logic board?

    What cable did you use to get the power from the optical drive bay?

    Thanks for the replies though, I know these questions can get annoying but I just don't want to damage the Mac Pro as its essential to my university work.
     
  6. Menel macrumors 603

    Menel

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    ATL
    #6
  7. pastrychef macrumors 601

    pastrychef

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    Location:
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    #7
    250W is more than 10% above 225W. Overclocked versions will obviously draw even more than 250W.
     
  8. AkuskaUK thread starter macrumors 6502

    AkuskaUK

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    #8
    So I should be ok using a 6 to 8 pin connector?

    Mines the normal version, not overclocked. Will it be too much? How can MVC say that it can be powered internally if it draws so high?
     
  9. Synchro3, Nov 8, 2016
    Last edited: Nov 8, 2016

    Synchro3 macrumors 68000

    Synchro3

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    #9
  10. superparati, Nov 8, 2016
    Last edited: Nov 8, 2016

    superparati macrumors member

    superparati

    Joined:
    Apr 11, 2016
    Location:
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    #10
    Hi AkuskaUK, here is the cable I ordered on the top of the card:

    2x data power to 6pin PCIe. here
    PCIe 6 pin extension cable 45mm. here
    Dual 6-pin PCIe to 8-pin power cable included within the pack. like that one
    2x min 6-Pin PCIe to PCIe here
     
  11. AkuskaUK thread starter macrumors 6502

    AkuskaUK

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    #11
    Everything is fine with no power downs? Have you ever had problems with it?

    Thank you, ill take a look :)
     
  12. pastrychef macrumors 601

    pastrychef

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    Location:
    New York City, NY
    #12
    Using a card rated at 250W will undoubtedly be pushing the power connectors beyond spec. Whether or not it's safe and/or acceptable is up to you (the consumer) to decide.

    There are quite a few users who use 250W rated video cards without issues. YMMV.
     
  13. Synchro3, Nov 8, 2016
    Last edited: Nov 29, 2016

    Synchro3 macrumors 68000

    Synchro3

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    Jan 12, 2014
    #13
    No problems, in Windows playing GTA V with high settings (no long shadows) and Starcraft 2 @ 4K without issues.

    In OS X El Capitan with latest drivers sometimes rarely fragments in videos, but this is a software issue.

    In macOS Sierra OpenCL issues solved.

    But never a Shutdown.
     
  14. AkuskaUK thread starter macrumors 6502

    AkuskaUK

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    #14
    Great to hear! Are you using a 6-8 pin adapter?
     
  15. h9826790 macrumors G3

    h9826790

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    Hong Kong
    #15
    I've did some tests about power draw by using 2x 7950. That can easily draw more than a single 980Ti. And here is the result.

    http://forums.macrumors.com/threads...or-approaching-silence.1982499/#post-23120938

    The cMP can practically deliver up to about 120W from each mini 6pin. However, I must say that officially NOT safe to do so. It works, I used this dual 7950 for more than a year already. As you can see from the test, even running Furmark on both 7950 at the same time, the cMP still survive. However, it's all up to you if you are happy to go beyond the official 75W limit. Once you go beyond that, nothing is safe technically.
     
  16. AkuskaUK thread starter macrumors 6502

    AkuskaUK

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    #16
    Thank you, ill have a read of that!
     
  17. JesterJJZ macrumors 68020

    JesterJJZ

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    Jul 21, 2004
    #17
    If you have a fully loaded tower like mine, you most certainly do need an external PSU for the 980ti. I have 6 internal drives, full RAM and 4 PCI cards. My tower would run for a few minutes then crash. External PSU fixed that.
     
  18. h9826790, Nov 9, 2016
    Last edited: Nov 9, 2016

    h9826790 macrumors G3

    h9826790

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    #18
    It's a simple supply vs demand calculation. The 980W PSU should be able to handle a fully loaded cMP.

    e.g.
    Logic board 80W
    CPU 130W x2 = 260W
    RAM 3W x8 = 24W
    980Ti 250W
    HDD 10W x6 = 60W (SSD will use much less)
    Super Drive 30W
    Fan 2W x5 = 10W
    PCIe USB 3.0 40W (all 4 port able to deliver 2A charge)

    All the above estimation is actual already on the safe side, and if stress everything together at the same time, it's about 750W, which still below the 980W rated PSU's limit. Unless you install another 980Ti (or another very power hungry PCIe card), the PSU should be fine.
     
  19. Synchro3 macrumors 68000

    Synchro3

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    Jan 12, 2014
    #19
    Yes, one 6 to 8 pin cable and one 6 to 6 pin cable.
     
  20. AkuskaUK thread starter macrumors 6502

    AkuskaUK

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    #20
    I have 4 internal drives, but thinking about dropping that to 2/3. I have full ram slots, but only 32gb.

    Thanks for this!

    Thank you!
     
  21. Shamgar macrumors regular

    Joined:
    Jun 28, 2015
    #21
    TDP is a rough design spec, not an exact measurement of power. In practice, a stock 980 Ti will draw much less than 250 watts. There are other 250 watt cards that won't work in a Mac Pro. Similarly, the 75 watts for each 6 pin power is the design rating, and in practice they can actually deliver more. The combination of those two margins means that a stock 980 Ti can safely be run off of 6-8 pin power in a Mac Pro. Many people are not comfortable deliberately biting into the design margins of the power supply and prefer to make other arrangements for power. I'm comfortable using my 980 Ti on a 6-8 pin cable, but I quite understand the caution of others.
     
  22. AndreeOnline macrumors 6502

    AndreeOnline

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    #22
    Is the 980 Ti up and running in Sierra or do we need to stay at El Cap or below?
     
  23. AkuskaUK thread starter macrumors 6502

    AkuskaUK

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    #23
    Thank you for explaining it :) I think I'm just going to go with a 6-8 pin adapter and run it from internal power :D
     
  24. pastrychef macrumors 601

    pastrychef

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    #24
    GTX 980 Ti works in Sierra wth the Nvidia web drivers.
     
  25. AndreeOnline macrumors 6502

    AndreeOnline

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    Aug 15, 2014
    Location:
    Zürich
    #25
    Cool.

    Found a new in box MSI GTX 980 Ti 6GB for $300 that I will try.
     

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