Radeon 5870 - Only 2 displays at a time??

Discussion in 'Mac Pro' started by slughead, Jan 29, 2012.

  1. slughead macrumors 68040

    slughead

    Joined:
    Apr 28, 2004
    #1
    I have 2 DVI monitors, an HDMI TV, an Apple brand Mini-display port to DVI adapter, and a 3rd party MDPort to HDMI adapter.

    Only a combination of TWO will work at once: both DVI monitors (one through the MDPort w/adapter), one of the DVI monitors through the MDPort + the HDMI TV, one of the monitors through the DVI port + HDMI TV. The 3rd display is always black.

    The DVI monitors are indentical-modeled Samsung 22" monitors (not dual link), the TV is 720p.

    Let me be clear: the 2 displays that do work, work PERFECTLY, whether it be the TV or the Samsung monitor. Even the HDMI audio works absolutely perfectly. I can plug in the 3rd display and that will work perfectly too as long as I unplug one of the others.

    I read a troubleshooting article whose solution was basically "yeah, don't use 3 monitors, derp"... Not what I bought this machine to do.
     
  2. digitalhen macrumors regular

    Joined:
    Jan 10, 2006
    #2
  3. alphaod macrumors Core

    alphaod

    Joined:
    Feb 9, 2008
    Location:
    NYC
    #3
  4. slughead thread starter macrumors 68040

    slughead

    Joined:
    Apr 28, 2004
    #4
    Alright, so I read a little about active Vs Passive and did a TON of googling. Here is what I found:

    This is a problem with the ATI cards themselves, not just Apple.

    It appears that the whole Active MDP -> DVI thing is pretty cheap and easy, but HDMI is more difficult.

    I love my HDMI audio and I'm not giving it up by using an Active MDP -> DVI then DVI -> HDMI. This puts me in a bind because there appear to be NO active MDP or DisplayPort -> HDMI adapters for sale at any price.

    I have a spare 4870... the problem is powering it with the 5870 in the case already. I just got this damn computer and already I'm rigging it to be as ridiculous as my last one.
     
  5. goMac macrumors 603

    Joined:
    Apr 15, 2004
    #5
    Get a GT 120. Cheap second card. No power issues.
     
  6. marcng macrumors member

    Joined:
    Jun 9, 2009
    #6
    my Moshi MDP-HDMI adaptor passes audio through with no problem.
    not sure if this is what you want.

    http://www.moshimonde.com/productDetail.aspx?group=19

     
  7. initialsBB, Jan 30, 2012
    Last edited: Jan 30, 2012

    initialsBB macrumors 6502a

    Joined:
    Oct 18, 2010
    #7
    As alphaod says, keep your HDMI as a passive connection. When I researched this a while back I understood that only the third connection had to be active, the other two can stay passive and it should work.


    OT Why is it that every time I click on an Apple KB article link I get a 404 error ? If I copy and paste the link it works.
     
  8. alphaod macrumors Core

    alphaod

    Joined:
    Feb 9, 2008
    Location:
    NYC
    #8
    That's why I said to use a DVI to HDMI adapter and hook up your DVI monitors to miniDisplayPort via active adapters.
     
  9. slughead, Jan 30, 2012
    Last edited: Jan 30, 2012

    slughead thread starter macrumors 68040

    slughead

    Joined:
    Apr 28, 2004
    #9
    That's not accurate, both MDP adapters have to be active to get 3 displays working, according to numerous articles including Apple's. Sapphire has an ATI card (6000 series??) that only requires 1 active adapter, but I have the stock Apple 5870 :(

    Yes I understand that, and it's a good thought.The problem is DVI has no audio, so doing DVI -> HDMI would effectively leave me with a video-only connection which is not acceptable unfortunately (GF hates my little speakers, wants to use TV's output).
     
  10. ActionableMango macrumors 604

    ActionableMango

    Joined:
    Sep 21, 2010
    #10
    Run a separate audio cord to the TV.
     
  11. slughead thread starter macrumors 68040

    slughead

    Joined:
    Apr 28, 2004
    #11
    I've decided to add another PSU and throw in my old 4870 to drive the extra monitor. I have the PSU, I have the card, I might as well use it (though not very elegant, it'll do the job).

    Thanks for your help, everyone!
     

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