attached 3rd monitor; now MP doesn't start up

Discussion in 'Mac Pro' started by malch, May 5, 2011.

  1. malch macrumors 6502

    Jan 20, 2008
    Hi there,
    I just attached a 3rd display (all Dells; one connected via DVI, the other two via DP->miniDP), and now my MP won't start up. None of the displays show anything (they stay black) and the MP doesn't make the chime after I push the button, as it should.
    Am I doing something wrong?
  2. dknightd macrumors 6502

    Mar 7, 2004
    try removing one monitor. see if you can see a pattern
  3. stefmesman macrumors 6502

    Jun 25, 2010
  4. Vylen macrumors 65816

    Jun 3, 2010
    Sydney, Australia
    If your MDP->DP cables are from Monoprice (or are the same as those from Monoprice) then that's your problem. Those cables are crap. They don't send a proper active signal or something when you start up.

    You need to get cables from at least Circuit Assembly.

    You can read about how we discovered everything about this in this thread.

    For now, though, to get your Mac Pro started, before turning it on, unplug the MDP/DP monitors so only the DVI monitor is in, and turn on the machine. Wait for the grey screen to appear on it and then plug in the other monitors again.
  5. malch thread starter macrumors 6502

    Jan 20, 2008
    Vylen, I think you're right about the bad cable.
    I've systematically connected my one working DP/miniDP cable to this new monitor, and alone, it starts up.
    I've tried the same thing with the DVI cable that I know works, and same thing, this monitor starts up fine.
    So I know all three monitors are working. I'm going to try to get a different cable (DP/mini-DP) and will see if all three work together.
    I'll report back. In the meantime, thanks for the advice.
  6. malch thread starter macrumors 6502

    Jan 20, 2008
    got a new DP cable with a DP/miniDP adapter, and all three monitors are working.
    Thanks for the help in sorting this out.
  7. jenzjen macrumors 68000

    Aug 20, 2010
    This is an over simplification, as I believe I posted in that thread as well. I have a 5870 driving 3 Dell 2410s all with monoprice cables with no issue, 1 dvi and 2 mdp/dp. The subtlety was with, at least Dell monitors, something in the xx11 model lineup that made it an issue.

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