24" iMac & Matrox DualHead2Go resolution question

Discussion in 'iMac' started by mgamber, Aug 14, 2009.

  1. mgamber macrumors 6502a

    mgamber

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    #1
    I bought a 24" iMac to replace my 18 month old Macbook Pro. It's nice and everything but it doesn't want to cooperate with my Matrox DualHead2Go and I'm wondering if anyone might know why. When I had it attached to the DVI port of the MBP I was able to use the MBP display and two external monitors, each set to 1680x1050. When I attach it to the iMac, it works but the best it will do is less...like each set to 1280x960 or so. Is the video card in the MBP really more capable or is it because the iMac has a much larger screen or is it something else I'm missing?
     
  2. Hellhammer Moderator

    Hellhammer

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    #2
    Be more specific please. Which 24" iMac? What GPU does it have? What GPU your MBP has?
     
  3. zmttoxics macrumors 65816

    zmttoxics

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  4. mgamber thread starter macrumors 6502a

    mgamber

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    #4
    Yeah, sorry, that occurred to me about 10 seconds after I hit Submit. The MBP has GEForce 8600M GT video with 256MB RAM, according to the system profiler. The iMac has GEForce GT 120 also with 256 MB of RAM. The iMac model ID is iMac9,1 at 2.93 GHz.

    The DualHead2Go is the digital variety and certainly capable of dual 1680x1050 since that's what I had it set to on the MBP. Oh...I forgot...could it also be a limitation of the DVI? The MBP has a full sized DVI socket while the iMac has that little thing that needs an adapter to attach it to anything in the real world. Currently I have one of the externals attached to that and another attached to a USB2->DVI adapter. It works, but it's not ideal.
     
  5. Hellhammer Moderator

    Hellhammer

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    #5
    Call to Matrox support
     
  6. zmttoxics macrumors 65816

    zmttoxics

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    #6
    Contact Matrox perhaps? Sounds like the drivers for the GT120 might not support it the same as the 8600M.
     
  7. mgamber thread starter macrumors 6502a

    mgamber

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    #7
    Think I should call Matrox support? ;)

    I read about that 1920x1200 resolution limitation with mini-dvi but I found it hard to believe that a desktop would be limited more than a laptop and thought I might be missing something. I suppose the resolution I was using was more or less the same number of pixels, however, so I suppose that's it. What a bummer...a nice, expensive machine like that throttled by a cheesy video adapter.

    Thanks for the replies!
     
  8. Hellhammer Moderator

    Hellhammer

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    #8
    No, it has Mini DisplayPort which can do 2560x1600. Sorry my last post was misleading, edited it. As zmttoxics said, it could be a problem with drivers

    I would give Matrox a call
     
  9. ADent macrumors 6502a

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    #9
    The MBPs can typically run the 30" ACD (2560 x 1600) while the iMacs and such can not and I would guess are limited to something in the 1920x1200 range.
     
  10. mgamber thread starter macrumors 6502a

    mgamber

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  11. Hellhammer Moderator

    Hellhammer

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    #11
    No, 2009 iMac has Mini Display Port so it can do up to 2560x1600 with dual-link DVI
     
  12. indg macrumors 6502

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    #12
    if your video card is capable of outputting the desired resolution, but os x isn't offering that resolution in the display preferences, you may need to create a custom resolution. try this:

    http://www.madrau.com/SRX3/html/SRX/About.html
     
  13. ADent macrumors 6502a

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    #13
    I guess I should have known since even the mini supports that now.
     
  14. mgamber thread starter macrumors 6502a

    mgamber

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    #14
    And 3360x1050 is a half million fewer pixels than 2560x1600 so it *should* work. In theory. I emailed Matrox support, if they come back with anything meaningful I'll post it. Per SwitchResX, I tried that and it was pretty worthless. It could force any resolution but offered no guidance whatsoever so none of the things it forced actually worked and I have no idea what the back porch timing of the card might be. :D
     
  15. mgamber thread starter macrumors 6502a

    mgamber

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    #15
    To follow up, I heard back from Matrox and they say it's a limitation of the mini display port. To quote: "The maximum stable resolution that we were able to obtain is 2048 x 768 (2 x 1024 x 768)."

    That sucks. If the MBP hard drive and FSB weren't so slow, I'd ditch the iMac and go back to the laptop.
     
  16. zmttoxics macrumors 65816

    zmttoxics

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  17. xcapepr macrumors newbie

    xcapepr

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    #17
    You should try using the $99 MiniDisplayPort to DUAL-LINK DVI adapter instead of the regular $29 one.

    The expensive adapter is the one that can run the 30 inch monitor full res. Without that one it can only go up to 1900 x 1200.
     
  18. zmttoxics macrumors 65816

    zmttoxics

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    #18
    Ooo! Excellent idea! :)
     

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