Running two video cards in OS X - Advantages?

Discussion in 'Mac Pro' started by urchinboy, Nov 3, 2008.

  1. urchinboy macrumors member

    Joined:
    Feb 8, 2008
    #1
    I have the option to get a free ATi 3870 video card in addition to my 8800gt. Primarily I work in FCP, Motion, Color and Photoshop. My instinct is to have the 3870 running both my 23" ACDs (one of which is fed through a Matrox MXO. Would there be any advantage in adding the 8800gt back into the system and running one display from each card? So the 3870 running display 1 and the 8800 running through the MXO to display 2.

    Would I be likely to see any improvement in things like Motion playback?

    Or is it just a really stupid idea on a wet Monday afternoon in London cos I'm a bit bored?

    All thoughts appreciated as always...
     
  2. IroquoisPliskin macrumors regular

    Joined:
    Oct 11, 2008
    #2
    The advantage would be each display has full run of its card's memory instead of having to share.
     
  3. dukebound85 macrumors P6

    dukebound85

    Joined:
    Jul 17, 2005
    Location:
    5045 feet above sea level
    #3
    you cant run two video cards in osx simultaneously like that for one thing
     
  4. IroquoisPliskin macrumors regular

    Joined:
    Oct 11, 2008
    #4
    Yes, you can. One display attached to each card.
     
  5. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #5
    I was under the strong impression you can only load a single set of video drivers. So mixing an nVidia card with an ATI card wouldn't be possible.

    Two of one manufacturer or the other, yes, though they can't run SLI or Cross Fire. Only independently. IIRC, this was discovered accidentally by another member or two on the forum, as the same driver pulled up different cards by the same GPU maker.
     
  6. Mackilroy macrumors 68040

    Mackilroy

    Joined:
    Jun 29, 2006
    #6
    It's quite possible, I've run a 7300GT and HD2600 XT simultaneously before.

    As for why you'd use two graphics cards, IP is right, each display would have all the memory available to use - though I recall around half a year ago someone showing a graphic that had the second display only using 12MB of RAM or so. Up to you, really. If it's free it can't hurt.
     
  7. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #7
    Under OS X, Windows, or both?

    To me, there's been a little confusion, and a definitive answer would be great.
    Thanks. :)
     
  8. urchinboy thread starter macrumors member

    Joined:
    Feb 8, 2008
    #8
    Thanks for replies. I'm talking strictly about running this in OS X.

    It just seems a bit of a waste to have a perfectly good video card just lying around in a box if I could be using it.

    Instinctively it seems odd to use an nvidia and ATi but if someone has managed it in OSX then I'll give it a try and see if it feels any better.

    Got to keep trying these things I guess.
     
  9. IroquoisPliskin macrumors regular

    Joined:
    Oct 11, 2008
    #9
    I had an ATI X1900 and NVIDIA 7800GT in my PowerMac G5.

    Do some benchmarks and tests on both as the primary display. The 8800GT is a great card but the ATi 3870 might do better in some applications. My old X1900 walked all over the 7800GT in OpenGL and Quartz.
    OpenGL Extensions Viewer, CINEBENCH and Xbench are great for graphics benchmarks.
     
  10. gotzero macrumors 68040

    Joined:
    Jan 6, 2007
    Location:
    Mid-Atlantic, US
    #10
    I use three of the 2600 cards to drive multiple monitors. I always assumed that the memory for each card was being used.

    I have never tried to pool the resources of the cards, they are not exactly graphics powerhouses anyway...
     
  11. Aea macrumors 6502a

    Aea

    Joined:
    May 23, 2007
    Location:
    Denver, Colorado
    #11
    It's definitely possible, considering you can even buy computers with multiple video cards (I'm referring to the MP here) directly from Apple.
     
  12. joegomolski macrumors 6502

    joegomolski

    Joined:
    Apr 28, 2006
    Location:
    So CA
    #12
    I have 2 30" ADC's. One is driven by my ATI 3870 card. The other 30" is using my ATI 1900.

    The difference in video performance, going from 2 ADC's and 1 card, and
    a separate ATI card for each ADC is noticeable.
     
  13. UltraNEO* macrumors 601

    UltraNEO*

    Joined:
    Jun 16, 2007
    Location:
    近畿日本
    #13

    You can load the MacPro with four different cards, giving you the option to drive eight thirty inch displays (provided your using suitable cards) Under MacOSX it'll be completely fine!! The system is intelligent enough to know what's the address used for each graphics card, therefore it'll attach each driver to each address.

    However... Under Windows XP Pro and Vista, it appears to be fine for two cards. Can't say what if you installed four though.

    I've tried both an ATI HD 2600 and as a side kick the 8800 GTS... and all is well! Technically speaking, the graphics card should deactivated if there's no display attached. Alternatively you can disable the card in the device manager!!
     
  14. UltraNEO* macrumors 601

    UltraNEO*

    Joined:
    Jun 16, 2007
    Location:
    近畿日本
    #14
    Umm... using two different cards, with two identical displays. Interesting.
    I would of though colour matching (if you need it) would be more difficult, since one of the cards might reproduce colour slightly warmer or cooler. Have you notice this?
     
  15. Mackilroy macrumors 68040

    Mackilroy

    Joined:
    Jun 29, 2006
    #15
    nanofrog: under both Leopard and XP, actually. XP fought it at first but eventually settled down. So you should be fine, urchinboy.
     
  16. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #16
    :cool:

    Thanks for the clarification. :)
    This might actually add a little hope for graphics options. ;) :p
     
  17. urchinboy thread starter macrumors member

    Joined:
    Feb 8, 2008
    #17
    Thanks for all the replies everyone. I'm a whole lot clearer on it now. :)
     
  18. fumanchu macrumors newbie

    Joined:
    Jan 30, 2008
    #18
    I have a Mac Pro with an 8800GT and an ATI 2600HD, I run two 23" displays off the 8800GT and a single 20" display off the 2600.

    Everything works great, but I wonder what's really going on when I run an OpenGL app, something like World of Warcraft. If I run the app in a window, I can drag it to any of the 3 displays. It even appears to run fine straddling between displays connected to the different video cards. It's.. amazing.

    However, I wonder what's really going on. Which GPU is actually processing the OpenGL? If I drag the window from the Nvidia to the ATI, does it actually transfer the OpenGL workload to the new GPU? If I drag the window to the new display, quit and then restart the app, will that cause it to start up using the new GPU? Or, is it always using the "primary" GPU and just sending the window contents to the other video card for display?

    Any insight appreciated :)
     
  19. murphx macrumors newbie

    Joined:
    Nov 8, 2008
    Location:
    Andover, Wiltshire, UK
    #19
    Hi mate, this is only a problem that exists in Windows (Vista for sure, couldn't say about XP).
     
  20. murphx macrumors newbie

    Joined:
    Nov 8, 2008
    Location:
    Andover, Wiltshire, UK
    #20
    I had a great setup with a quad 2.0 using 1x ATI X1900XT and 2x nVidia 7300GT in OS X with a 22" widescreen running off each one in OS X.

    Under Vista, only the X1900XT (center monitor for this reason!) was usable at all. I use Windows for gaming.
     
  21. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #21
    Mackilroy (couple of posts up) beat you to it. :p

    He also indicated XP will work with cards from different manufacturers, though not without a tantrum or two. ;) :)
     

Share This Page