"crossfiring" flashed cards ? (6870)

Discussion in 'Mac Pro' started by MaxHarryson, Jul 1, 2011.

  1. MaxHarryson, Jul 1, 2011
    Last edited: Jul 1, 2011

    MaxHarryson macrumors newbie

    Joined:
    Jun 23, 2011
    #1
    Some months ago now ( iam slow in fixing stuff ;P) my 8800 gt for my mac pro 2008 died and i need to buy a new card.
    Mac wants me to buy the 5870 for abour 4500 sek (650ish dollars) or the 5770 for about half the price. None of these cards is what i want.
    So i read this: http://www.groths.org/?p=297
    and some other posts (including some from this forum) that said that it will work w/o flashing (Making the title of this post misleading), only with special installed drivers.
    These cards are about 1700 sek so I can take the graphics card from my dads old, old mac pro and put it in mine install the driver, then put in the 6870. Would getting 2 of these work ? (crossfiring) and would i get increased performance ?
    I only really care about my W7 partition, the Mac partition is less important, i only need one card to work there.


    *edit*
    I just read something about steam crashing ? Is this true ?
     
  2. ActionableMango macrumors 604

    ActionableMango

    Joined:
    Sep 21, 2010
  3. Cindori macrumors 68040

    Cindori

    Joined:
    Jan 17, 2008
    Location:
    Sweden
    #3
    In Windows, yes.

    http://www.groths.org/?p=431



    To power the cards you need 4x PCIe 6-pin cables. The Mac Pro has special outlets for 2 of those on the motherboard. To use those you need special cables, which you can get from Apple Store for like 200sek each, eller köpa av mig för 100kr st gratis frakt, har dock ej tillgång till dem föränn i augusti (flyttat under sommaren).

    The second 2 power cables you can route from the second superdrive slot, see my signature...
     
  4. MaxHarryson thread starter macrumors newbie

    Joined:
    Jun 23, 2011
    #4
    So, how many cables to i need total ? 4 ? and can i connect the extra 2 to an external power source or something ?
     
  5. Cindori macrumors 68040

    Cindori

    Joined:
    Jan 17, 2008
    Location:
    Sweden
  6. MaxHarryson thread starter macrumors newbie

    Joined:
    Jun 23, 2011
    #6
    Yes, but i didnt quite get it.

    So, could you please send me a link to those cables ? I couldnt find them on apple store ? And do i have enought outlets or not :S The one thing i dont get about computers is the graphic card plugs and needs because i´ve had to swap one before
     
  7. Cindori macrumors 68040

    Cindori

    Joined:
    Jan 17, 2008
    Location:
    Sweden
    #7
    its not available on the apple store, its a spare part, they can get it if you ask for it


    Read the golden guide in my sig.
     
  8. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #8
    The power cables needed to connect to the logic board can be found here.

    But I'm under the impression you'll need 4x 6 PSIG connectors for both cards, and the logic board will only provide 2.

    The best way to go about taking care of this, is via a second PSU. Either use a standard computer PSU and jump the green and black wires (gets it to power up), or use something like a Juice Box that will fit in the empty optical bay (IIRC, there's 2 versions; 300W and 450W - they've been used by other members successfully in MP's before). The second computer PSU is cheaper, but also less attractive (sits outside of the MP with cables routed internally to the MP).

    Others have used Y splitters on the PSIG ends, but that could draw too much current over the PCB traces on the logic board and system's PSU (there has been at least one instance where someone did this, and fried their system, so this is why I don't recommend trying the Y splitter method).

    Hope this helps. :)
     
  9. MaxHarryson, Jul 1, 2011
    Last edited: Jul 2, 2011

    MaxHarryson thread starter macrumors newbie

    Joined:
    Jun 23, 2011
    #9
    Also, i think my mac pro has ios 10.5.x, will it still work or do i need to upgrade ? Also, if i only get one card, will i hav enought outputs to run it ? (just making sure)
     
  10. MaxHarryson, Jul 2, 2011
    Last edited: Jul 2, 2011

    MaxHarryson thread starter macrumors newbie

    Joined:
    Jun 23, 2011
    #10
  11. nanofrog macrumors G4

    Joined:
    May 6, 2008
  12. MaxHarryson thread starter macrumors newbie

    Joined:
    Jun 23, 2011
    #12
    Do i need to install the injector thing before or after i put in the card ?
     
  13. lesliekkwu macrumors newbie

    Joined:
    Dec 28, 2008
    #13
    Hi Cindori,

    Have been a fan using your zeus since my first mac pro 1,1 for ati 4890! great work !

    Regarding your signature of mac pro power, will it be possible for mac pro 2010 ?

    thanks !
     
  14. ghislain macrumors member

    Joined:
    Apr 22, 2009
    #14
    I am not sure

    Like HD slots, the superdrive slots are meant to support 5 watts (25 max), not 150. It is true that it works (I tried it with an additional 5870). However, I think that the additional card only works in the "low energy mode" and will be useless in crossfire. Moreover, it may deteriorate PSU in the long term (errors are detected in Hardware tests), so I would not recommend it.
     

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