5870 and 5770 power

Discussion in 'Mac Pro' started by ima747, Sep 17, 2012.

  1. ima747 macrumors newbie

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    Sep 17, 2012
    #1
    Been doing some reading and I've got some conflicting information, reaching out for more insight.

    I would like to run a 5870 and 5770 in my mid 2010 mac pro. The core issue is that the system has 2 PCI-e 6 pin power adapters, the 5870 needs 2 and the 5770 needs 1.

    The 2 resolutions I've found are:
    1) Add a second PSU
    2) Split one of the 6 pin connectors with a Y adapter

    The PSU will work, plenty of power, however it's another PSU, that's space, expense, weight, power draw, complexity, etc.
    The splitter should work (according to people claiming to have used it), and the system's PSU should have more than enough power to run both cards even under load.

    I'm inclined to think that the Y adapter will work fine (I've seen plenty of PC configs that include splitters for their graphics cards). But it's still kinda sketchy since the 5870 has 2 plugs, there are 2 plugs... you're draining some of that capacity from one plug for the 5770...

    Thoughts, insights, etc. Not looking for "PSU is safer" or anything vague like that, but if there's a real problem with the Y adapter approach what is it specifically. Are there not enough amps under full load of both cards due to a limit on the draw of each connector or what? Would an issue only be likely to show up under a certain config (full 6 monitors, only if all 6 were running full dual link resolutions?) or under certain situations (maxing out the 5870 and then begin maxing out the 5770, the 5870 gets starved and crashes?).

    Any reasoned insights would be greatly appreciated!
     
  2. ActionableMango macrumors 604

    ActionableMango

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    Sep 21, 2010
    #2
    Don't do it. This post explains it pretty well.

    To summarize, the power from the PSU goes through traces in the logic board and out wires of a certain size. When you add a y-cable, the PSU may be fine, but the traces and wires leading up to the y-cable are now trying to carry twice as much power as they were designed for.
     
  3. ima747 thread starter macrumors newbie

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    Sep 17, 2012
    #3
    Perfect, thanks! A documented reason, not just speculation.
     
  4. bax2003, Sep 18, 2012
    Last edited: Sep 18, 2012

    bax2003 macrumors 6502a

    bax2003

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    Belgrade, Serbia
    #4
    Interesting but, combo with 4870x2 and a 9800GX2 is MUCH more power hungry than 5870 + 5770.

    This guy had 5770 + 5870 long time, and now he has 5870 + 5870 for more than 18 months.
    http://www.youtube.com/watch?v=ui6q_6k1vxA

    Numbers are: (load power consumption)

    GeForce GX2: 186W (8 + 6 pin)
    Radeon 4870 X2 320W (8 + 6 pin)
    Together: ~505W

    Radeon 5870: 240W (6 + 6 pin)
    Radeon 5770: 122 W (6 pin)
    Together: ~360W
     
  5. MacVidCards Suspended

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    Nov 17, 2008
    Location:
    Hollywood, CA
    #5
    Except I wasn't running the GX2 and 4870x2 together. I was pointing out that either one ALL BY ITSELF could overload the Mac Pro. I did what many do and used a 6 to 8 pin adapter to run the 8 pin.
     
  6. The-Pro macrumors 65816

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    Germany
    #6
    You beat me to it mate.
    I wanted to write that about running the two 5870's using y adapters from that person on youtube.

    MacVidCards, is that your youtube channel?
     
  7. dmax35 macrumors 6502

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    Jun 21, 2012
    #7
    My neighbor tried (2) 5870 in his Mac Pro for awhile and noticed a great deal of heat build up and reverted back to running dual 5770's.
     
  8. ima747, Sep 18, 2012
    Last edited: Sep 18, 2012

    ima747 thread starter macrumors newbie

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    Sep 17, 2012
    #8
    The core of the issue, according to the post linked in the second post, is that the 6 pin plugs on a MacPro actually pass through the motherboard. That means they're not just wires, they're actually traces in the board. As a result they're more sensitive to overdraw (there's less metal for power to pass through, so passing more electricity can theoretically cause damage).

    The PSU should be able to take it, but the traces in the motherboard might not over time. It *will* work with a Y adapter. It won't harm your power supply. But it *might* (very big might) hurt the traces on the motherboard, which in turn could hurt the graphics cards if the traces go bad. So, ultimately this is do at your own risk. A MacPro is a very very pricey piece of kit to replace so if you cook out a portion of your motherboard and can't run one or both of your nice graphics cards that's a problem.

    I can't find any records of *anyone* having a problem with the Y adapter config. (please link if you have info!) That doesn't mean it's safe, that means it work. A second PSU is definitely the safer choice, but if you're willing to take the (seeming limited) risk it is by far the easier and cleaner option.

    ----------

    The 5870's draw almost twice the power than the 5770, which means far more heat. The bigger problem is with dual 5870's, unless you modify them, the lower card's fan will be blocked by the upper card. This isn't a problem with a 5770 above a 5870 according to what I've read because the support loop at the back of the 5770 allows the 5870 bellow to breath.

    You can modify the 5870 to give it a new air hole, but whenever you take tin snips to something electronic it's definitely going to have a negative impact on your warranty :0)

    The heat + power draw + expense + I only need one high performance card (second if just for extra screens while working) is why I'm leaning towards a 5870/5770 mix.
     
  9. jenzjen, Sep 18, 2012
    Last edited: Sep 18, 2012

    jenzjen macrumors 68000

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    Aug 20, 2010
    #9
    I have the 5770/5870/Y splitter setup and have had no issues, but I'm not stressing my GPUs (no gaming, rendering, etc) just needed 3 screens for general work stuff.

    If you only use Mac OS, you should try the Atlona DP400 before buying another card.

    Under Windows, something between Windows, ATI and Atlona = can't get native 27" resolution to the 3rd monitor but works fine under Mac OS.

    Note, 5870 fan is pretty much blocked by the 5770 card. Watch the YT video from earlier posts, or look at this picture http://blog.macsales.com/tag/5770
     
  10. ima747 thread starter macrumors newbie

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    Sep 17, 2012
    #10
    The atlona does look like a nice option for simply "more screens". Personally however I'm already running 3 off the 5770 (21") and am looking to add another 3 (27") on the 5870. Further I do use it for gaming, and rendering so more more more is what I'm after :)
     
  11. spaz8 macrumors 6502

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    #11
    I've been running 2x 5770's in my MP 1,1 without issue for almost 2 years now.
     
  12. ima747 thread starter macrumors newbie

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    Sep 17, 2012
    #12
    5770 x2 is a stock config, and doesn't require 3+ 6 pin GPU power connectors
     
  13. lixuelai macrumors 6502a

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    Oct 29, 2008
    #13
    Better question is why do you need a HD5770 if all you are doing with it is using it for extra display outputs.
     
  14. ima747 thread starter macrumors newbie

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    #14
    See post #10
     
  15. lixuelai, Sep 18, 2012
    Last edited: Sep 18, 2012

    lixuelai macrumors 6502a

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    Oct 29, 2008
    #15
    The HD5770 is not going to help you for gaming and I doubt it does anything for rending. The primary card does all the work though I may be wrong on the second count. Anyway in all likelihood you are not using the HD5770 for much and can get away with a cheaper and lower power consumption card. That said though the HD5770 has 3x outputs and the best alternative that is natively Apple is the GT 120 which only has 2. Of course you can get like 2x GT 120 by selling the HD5770 but you may need the PCI-E ports.

    p.s. If you are feeling adventurous you can get the HD5870 Eyefinity 6. It is known to work in Lion with all 6 outputs. Not sure about ML.
     
  16. jenzjen macrumors 68000

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    Aug 20, 2010
    #16
    Should have been more clear, to support 3 27 ACD only options are 2 cards or the DP400 (Mac only). For most other displays, driving 3 off either 5770 or 5870 not an issue.
     
  17. Redneck1089 macrumors 65816

    Redneck1089

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    #17
    Maybe I am just being ignorant, but why not just run the second GPU from the second CD drive bay? That is what I am doing for my 5870 and my 4870 in my Mac Pro 1,1.
     
  18. ActionableMango macrumors 604

    ActionableMango

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    Sep 21, 2010
    #18
    OP, if it's your personal property you can certainly go ahead and do this as long as you are aware of the risk.

    Also I thought I would mention an alternative you may or may not know about already. There are inexpensive secondary PSUs that install in the CD bay and automatically turn on and off with the main PSU (by detecting power from a drive connector on the main PSU). It is a much more clean solution than running an external PC power supply.
     
  19. Redneck1089 macrumors 65816

    Redneck1089

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    Jan 18, 2004
    #19

    So are you saying that you still require a separate PSU even if you run power from one of the disk drive bays to a second card?
     
  20. slughead macrumors 68040

    slughead

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    Apr 28, 2004
    #20
    In a few days when I get my extra PSU I'll make a how-to on making a regular PC PSU into a modular external PSU for a mac pro. I've already built one which has been working great for a year.

    Others have mentioned the drive-bay PSU--not sure how you're going to get the power cable in the case for that ( can someone who has done it post how? ). Also, regular PC PSUs are less expensive.
     
  21. ActionableMango macrumors 604

    ActionableMango

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    #21
    Separate issues. What I'm talking about is not related to using disk power at all.

    Sure, the instructions are here.
     
  22. ima747 thread starter macrumors newbie

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    Sep 17, 2012
    #22
    The drive bay PSU is the method I will take if I choose to play it on the safe side. Apologies, I should have clarified this some time back I suppose. An external solution would be very much sub-optimal as it would require either heavily modifying the case, or leaving the side off which would GREATLY affect the air flow and cooling capacity (Apple put some serious work into their cooling design on the Pros) which could be just as bad as the Y adapter, especially if someone was opting for dual 5870s... poor cooling = cooked hardware, I've been there many times with my PC's :0)
     
  23. slughead macrumors 68040

    slughead

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    #23
    Oh I see, he modified the case with tin snips.
     
  24. Redneck1089 macrumors 65816

    Redneck1089

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    #24

    But do you know if it would work powering a GTX 580 from the disk power?
     
  25. ActionableMango macrumors 604

    ActionableMango

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    Sep 21, 2010
    #25
    I have no idea.

    I think the 6-pin video power connector is rated for 75 watts. If you can find out how much the SATA power connector is rated for, that would give you an answer.
     

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