So SLI in Windows with GTX 285 or not?

Discussion in 'Mac Pro' started by justflie, Jun 1, 2009.

  1. justflie macrumors 6502a

    justflie

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    #1
    Hey all,

    Given that it appears the GTX 285 "Mac Edition" is on the horizon (June 3rd?), can the mac pro physically (ie power, space, cooling) handle 2 GTX 285s in SLI in Windows?

    I understand that OS X does not support SLI so I wouldn't expect any performance gains there. Would it just ignore the card in slot 2 when I boot into OS X?

    Thanks for your info, I plan on ordering one (or maybe 2) when I get your answers. :apple:
     
  2. Tallest Skil macrumors P6

    Tallest Skil

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    #2
    Can't be done. The hardware itself disallows it.

    You would need to use all of your PCIe slots and one ODD bay to have both cards.
     
  3. justflie thread starter macrumors 6502a

    justflie

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    #4
    *tear. My wallet thanks you, but not my heart :)
    :D
     
  4. Spanky Deluxe macrumors 601

    Spanky Deluxe

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    #5
    Unfortunately nVidia also limit what motherboards SLI can use far more than ATI does. The only nVidia cards that you could link together via SLI were the original 7300GT cards and you had to use some hacked drivers for that. Its for this reason that I will never buy an nVidia card for my Mac Pro. The 4870 is only a little slower than the GTX 285, if anything depending on the drivers, yet I can use two flashed 4870s in Windows in Crossfire giving far superior performance than a single GTX 285.
     
  5. justflie thread starter macrumors 6502a

    justflie

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    #6
    Spanky, how did you hook up the power (second card) for the crossfire solution? This would certainly be a cheaper way to go for me so any details would be appreciated.
     
  6. Spanky Deluxe macrumors 601

    Spanky Deluxe

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    #7
    I simply used two PCIe Y-Splitter cables. They'd be easy to make yourself but I ponied up the money and found someone that sold them. I've got a power lead running down from the optical bay with which I powered a PC 3870 before but I prefer using the Y-splitters. No problems so far on my 2006 Mac Pro. If you go this route, make sure you get two PC 4870s and flash them, it looks like Apple has manually disabled Crossfire in the Mac 4870's bios.
     
  7. justflie thread starter macrumors 6502a

    justflie

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  8. seisend macrumors 6502a

    seisend

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    #9
    wuuup?

    I've seen Game Benchmarks with the GTX 285 a few frames faster than than the ATI 4870 X2 ! But average the 4870 X2 is 10 FPS faster than the 285. And the GTX 285 is average like 10 FPS faster than the 4870.

    Watch Benchmarks here, there are a few pages of tests.

    http://www.tomshardware.com/de/Nvidia-Geforce-GTX-275,testberichte-240299-8.html
     
  9. Spanky Deluxe macrumors 601

    Spanky Deluxe

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    #10
    You can't use Crysis as a fair comparison. Its well known that its heavily coded for an nVidia advantage and Crossfire hardly works with it. Its an awefully coded game and a not very fun one at that. Look at any of those benchmarks apart from Crysis and GTAIV, which is probably the worst coded port of all time and a 4870X2 setup is at the very least on a par as a 285 and is usually significantly faster at 2560x1600.

    As an incredibly rough comparison but far better than just looking at Crysis, you might want to look at the "Sum of All Frame Rates" results page. In particular the lower graph for very high details, 4x AA, AF.
     
  10. seisend macrumors 6502a

    seisend

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    #11
    I know Crysis is a "nvidia game". It's always the same, some games have ATI in the back , othes nVidia.. I don't like this Sum of all comparisation. Doesn't say much for me. I think my comparisation with the 10 FPS wasn't that bad ;-):


    Comparisation (of toms hardware Sum Comparisation)

    GeForce 285 GTX @ 1680x1050
    54 FPS faster than 4870 / 16 FPS slower than 4870X2

    GeForce 285 GTX @ 1920x1200 -
    62 FPS faster than 4870 / 41 FPS slower than 4870X2

    GeForce 285 GTX @ 2560x1600 -
    73 FPS faster than 4870 / 76 FPS slower than 4870X2

    As you see, the overall diffrence between the 4870 and 285 is much bigger than the diffrence between the 285 and 4870X2.
    I think most people use at the moment 1920x1200 resolution or lower.

    Don't know but maybe is it the better choice to get two 4870 crossfire* than one 285 gtx.Cause the 285 mac edition is very expensive ATM.
    Or try a 4870X2...
    (* I am not sure if the mac pro supports crossfire under bootcamp windows)
     
  11. justflie thread starter macrumors 6502a

    justflie

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    #12
    So is a GTX 285 the best possible graphics card for a Mac Pro at this point? I've been reading that, since 10.5.7, it's relatively easy to get an ATI 4890 up and running in both Windows and OS X. As far as I understand it, the GTX 285 is > ATI 4890.

    That being said, is it possible to run a crossfire of 2 x 4890's or is there not enough power/connectors available to pull it off?

    Thanks for all your help. I've been away from the PC building world for about 5 years so I'm a bit out of the loop :p

    Also, it seems as if a new generation of cards (from ATI and Nvidia) is right around the corner. It's making me start thinking twice about this purchase.
     
  12. Spanky Deluxe macrumors 601

    Spanky Deluxe

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    #13
    True, more people use 1920x1200 than 2560x1600 but then a game that comes out next year would likely need a similar amount of graphics power to drive 1920x1200 as a similar game would need now to drive 2560x1600.

    A 285 is definitely faster than a 4870 in Windows and a 4870x2 setup is definitely more powerful than a 285 in Windows most of the time. As you say, the 285 Mac Edition and even the 4870 Mac Edition are very expensive at the moment. However, you can get two 4870 PC cards for roughly the same as one 4870 Mac Edition card.

    I don't think anyone's tried 2x4890s in a Mac Pro yet. Mind you, I don't think the 4890s are worth the extra money. Although they're new chips, slightly new design, one could say they're just 4870s with faster clock speeds at a significant price premium. Although 4890s do work in OS X, you have to install a patch that could very well break in future versions of OS X, requiring you to wait for an update. Whereas a flashed 4870 should, in theory, be far more resilient to updates since Apple officially supports a 4870 card.

    The GTX 285 is currently the best single GPU graphics card that you can get that will work in OS X. In theory, at least. I'd wait for reviews and benchmarks to arrive before purchasing though. NVidia's OS X drivers have been so poor in the past that far cheaper ATI cards have surpassed them in Core Video applications. I'm hoping they've sorted things out this time around but only time will tell.
     
  13. justflie thread starter macrumors 6502a

    justflie

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    #14
    Thanks, Spanky :) Your handle makes me want to dig out Little Rascals from someplace.
     

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