Why no 2X ATI Radeon HD 5870 on BTO page?

Discussion in 'Mac Pro' started by sparkie7, Aug 19, 2010.

  1. sparkie7 macrumors 68000

    sparkie7

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    Oct 17, 2008
    #1
    Theres 2X 5770 but not for the 5870 -- is it b/c of the power draw requirements?
     
  2. peskaa macrumors 68020

    peskaa

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    #2
    Yes, and not enough feeds off the logic board to provide the power.
     
  3. sparkie7 thread starter macrumors 68000

    sparkie7

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    Oct 17, 2008
    #3
    ok thanks. there's no 1x of each, so assuming there's not even enough power to run one of each. bummer..

    what's better 2x 5770's or 1x 5870 -- to drive 3x 30 ACD's

    I assume its the 2x 5770's?
     
  4. DigitalVT macrumors member

    DigitalVT

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    #4
    Well I ordered mine with one 5770 with the idea of adding a 5870 later when they become available, surely there will be enough power for this!!!
     
  5. peskaa macrumors 68020

    peskaa

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    #5
    There are two feeds off the board in total. The 5770 uses one, so you can have two cards. The 5870 uses two, so you can only have that single card installed.

    The way round it, of course, is to install a 5870 and then have a GT120 (or several) for extra screens, as they don't need power feeds and OS X copes fine with a mix and match of GPU vendors.

    For running three 30"ers, yes, the pair of 5770s. You can't Crossfire the boards, but you'll get better performance on a whole.
     
  6. DigitalVT macrumors member

    DigitalVT

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    #6
    I was thinking of getting maybe a third power feed off of the unused (2nd) CD/DVD tray??
     
  7. Cindori macrumors 68040

    Cindori

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    #7
    i thinks thats sata power, dunno if there are adapters
     
  8. nanofrog macrumors G4

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    May 6, 2008
    #8
    The best way to safely run a second 5870 (or 5770 + 5870, or even 2x 5770's + 1x 5780), is to run a separate power supply.

    The easiest way to do this, is by using a graphics card PSU that's meant to fit in a 5.25" bay (here). Cheap too. If the second optical bay is used, then run it externally (not pretty, but better than a PC PSU due to the mess of unused wiring, and no need to jump the green and black wires to make it work).

    As per the idea of pulling the power from the backplane connector located at the empty optical drive (power + data), I wouldn't recommend it. It's not likely to be able to provide sufficient current, and could actually damage the system.

    Nor would trying PSIG Y splitters (again, too much current on the rail, and in this instance, melt the solder for the traces on the backplane board = short circuit, resulting in a new backplane board needed; board that has the PCIe slots on it).
     
  9. Inconsequential macrumors 68000

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    Sep 12, 2007
    #9
    Seems like a waste of time, money and energy when the Mac Pro has a 1200W PSU available.

    I'm sure you could make or find some adapters that can draw the power off the SATA connectors... :p

    Edit: Assuming the SATA connectors have a decent enough power rating.

    If your really brave then opening up the PSU to take another feed off there would be a way forward :p Although warranty issues!
     
  10. peskaa macrumors 68020

    peskaa

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    #10
    And the cabling for such would be a nightmare. Finding space for optical drive into PCIe bay leads is hard enough...
     
  11. Cindori macrumors 68040

    Cindori

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    #11
    there is hole in the optical area bottom that comes out at 1st harddrive
     
  12. barefeats macrumors 65816

    barefeats

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    Jul 6, 2000
    #12
    Brilliant. In the past, I used an external modified ATX 500W power supply to drive dual GPUs that required two power feeds each. It was not a pretty sight with the side cover off and power cables running from the ATX to the PCIe bay.

    The Optical Bay PSU is a more elegant solution if you want to run dual 5780s. If you are running Windows via Boot Camp, you should be able to jumper them with a CrossFire connector (assuming that connector isn't covered up).
     
  13. Transporteur macrumors 68030

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    Nov 30, 2008
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    UK
    #13
    That way you'd block the first hard drive and you wouldn't be able to slide in the optical bay any more.

    There is however allocated space around the upper left corner of the logic board. The optical bay SATA cables also run through there and there is more space for additional cabling.
    All it takes is to disassemble the front PCIe fan and the supply cable cover behind the optical bay.

    There is, however, no way to force two 6 pin connectors through there. Taking of the connectors should work though.
     
  14. Cindori macrumors 68040

    Cindori

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    #14
    wtf u talking bout? :)

    <log in to see this pic>
    [​IMG]
     
  15. Transporteur macrumors 68030

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    UK
    #15
    :p
    Unfortunately I can't see anything on that pic. I just made a quick one.

    [​IMG]

    As you can see the '09 and thus the '10 models don't have any holes in the bottom plate. You can however access the ODD bay through the space on the left.
    All you have to do is remove the power supply cable cover and the front PCIe fan.
     
  16. Cindori macrumors 68040

    Cindori

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    #16
    hm. well it seems that the hole is still there but there is a cover on the back, hiding it. then we are speaking of the same hole. good pic.

    at least on the 06 you could fit a cable there. but yeah it's tight, took me about 10min to force a molex through.
     
  17. Spanky Deluxe macrumors 601

    Spanky Deluxe

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    London, UK
    #17
    You can buy six pin pcie power cable y-solitudes to power two 5870s. Of course, you'd be running more power through the tracers on the board than they were specified for. I remember people having some stability problems powering a second card from the optical bay but I ran two 4870s in this manner in my Mac Pro for about seven months without issue before upgrading.
     
  18. nanofrog macrumors G4

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    May 6, 2008
    #18
    It's to do with how the +12V rails are used.

    There's no actual statement of the PSU size in the specification page, just voltage and current consumption (which are peak values BTW). But even if it actually is a 1200W unit, that's likely a peak rating, not a continuous one. So take that number and divide by SQRT 2 (1200W/1.414) = 850W. If it's the same as previous models (980W), then the continuous power rating would = 980W/1.414 = 700W.

    Yes, there are adapters out there (indirectly, so multiples would be required; and possibly modified for gender).

    They don't. Worst case, it's meant to handle ~40W (peak power draw of a mechanical drive during spin up).

    You'd need to know what rail goes where, what the current load is on each, and what they're rated for in order to determine you can draw sufficient power. You can't just tie them together either, as the voltage regs usually are not using matched components (transistors for example) = uneven power draw that will burn one, then the other out.

    I recall one person for sure that tried this, and burnt out their board. :eek: The solder on the traces melted, causing a short that in turn, burnt it out. :(

    Not good IMO.
     
  19. Justinf79 macrumors 6502

    Justinf79

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    Oregon
    #19
    So can OS X use both the GT120 and 5870 together in OpenCL stuff?

    Also, how will Win7 handle this setup? I ask because I have a GT120 atm, and thinking about getting the 5870 when it's available.
     
  20. cured.not.dried macrumors member

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    Nov 23, 2008
    #20
    gt120 doesn't do openCL

    and windoze hates cards from different vendors being present, although you should just be able to disable the gt 120 in the devices control panel.
     
  21. cured.not.dried macrumors member

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    Nov 23, 2008
    #21
    how would one power that 5.25" bay PSU without leaving the case open? i'm really interested in this, but i don't wanna have my case open cause kitty loves to rub up on my computer when i don't pay attention to her...
     
  22. Justinf79 macrumors 6502

    Justinf79

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    #22
    Actually the GT120 is supported.
    http://www.apple.com/macosx/specs.html :)
     
  23. goMac macrumors 603

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    Apr 15, 2004
    #23
    Uh, no, the GT 120 most certainly DOES do OpenCL. I've used OpenCL on my GT 120.

    http://www.nvidia.com/object/io_1252000156987.html
     
  24. Vylen macrumors 65816

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    #24
    There's no 2x 5870 option because doing so would set your Mac Pro on fire...

    On a related note, just how much heat do they generate? :p
     
  25. goMac macrumors 603

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    Apr 15, 2004
    #25
    Also, I should mention that VISTA hated cards from different vendors, that was fixed in Windows 7.
     

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