triglyph

Q: Connecting HDMI takes out one of my monitors.

I have three monitors - one Apple Cinema Display and two DVI monitors. When I connected a cable from the HDMI output (to a receiver) I do get a picture on the TV, but one of my DVI monitors is blanked out.

 

None of the monitors is Thunderbolt/Displayport so they are using adapters. Is that the problem?

Mac Pro, OS X Yosemite (10.10.5), The new Mac Pro

Posted on Feb 2, 2016 4:36 PM

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Q: Connecting HDMI takes out one of my monitors.

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  • by Grant Bennet-Alder,Helpful

    Grant Bennet-Alder Grant Bennet-Alder Feb 5, 2016 1:02 PM in response to triglyph
    Level 9 (60,909 points)
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    Feb 5, 2016 1:02 PM in response to triglyph

    You may have TWO legacy displays hooked up using passive adapters. If you choose the built-in HDMI that counts as one. Beyond that, legacy displays require ACTIVE adapters.

     

    "legacy" in this context is anything other than Mini DisplayPort or DisplayPort (a direct re-wire, not a conversion).

     

    To debug, try using only two displays. If it is working then, you need an ACTIVE adapter for something to make additional progress.

  • by Malcolm J. Rayfield,Apple recommended

    Malcolm J. Rayfield Malcolm J. Rayfield Feb 5, 2016 1:02 PM in response to triglyph
    Level 5 (7,945 points)
    Feb 5, 2016 1:02 PM in response to triglyph

    Make sure you don't have more than two displays on one Thunderbolt bus.  The HDMI port is on the same Thunderbolt bus as the bottom two Thunderbolt ports.

    https://support.apple.com/HT202801

  • by triglyph,

    triglyph triglyph Feb 5, 2016 1:04 PM in response to Grant Bennet-Alder
    Level 1 (95 points)
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    Feb 5, 2016 1:04 PM in response to Grant Bennet-Alder

    Thanks to all. This answers the question, but leaves me with a quandry. The reason I wanted to use the HDMI port is because all my Thunderbolt outlets are used up.  Is there any such thing as an active HDMI to HDMI? Haven't found one.

     

    Only one possibility, I do have a Sonnet Echo 15 which has an open Thunderbolt but I would really like to use the HDMI output somehow. Any thoughts?

  • by triglyph,

    triglyph triglyph Feb 5, 2016 1:06 PM in response to Malcolm J. Rayfield
    Level 1 (95 points)
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    Feb 5, 2016 1:06 PM in response to Malcolm J. Rayfield

    Thanks for the feedback. Does the Mac Pro have more than one Thunderbolt bus are all they all together?

  • by Grant Bennet-Alder,Apple recommended

    Grant Bennet-Alder Grant Bennet-Alder Feb 5, 2016 2:09 PM in response to triglyph
    Level 9 (60,909 points)
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    Feb 5, 2016 2:09 PM in response to triglyph

    The underlying issue is the amount of power available on the single power lead available on the interface. Once you try to go beyond two, you are out of power.

     

    There are two solutions that come to mind:

    1) use the sonnet echo 15 to run a display. Your power budget should start over. But that means you cannot chain another ThunderBolt device off the sonnet echo 15.

     

    2) on the Mac Pro chassis, use an ACTIVE adapter to Single-Link DVI (for up to about 1920 wide). This one is well known and works, about US$40 at amazon:

    http://www.amazon.com/StarTech-com-MDP2DVIS-DisplayPort-Active-Adapter/dp/B004SU ELLC/ref=sr_1_14?ie=UTF8&qid=1454709758&…

     

     

    .

  • by mdesignffm,

    mdesignffm mdesignffm Feb 5, 2016 4:57 PM in response to Grant Bennet-Alder
    Level 2 (306 points)
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    Feb 5, 2016 4:57 PM in response to Grant Bennet-Alder

    i have the same problem.

     

    sorry, i do not get this: the star tech adapter has no additional power, it derives its power from thunderbolt. so how can it solve the actual problem that there is only power for 2 HDMI/DVI devices?

     

    the original apple adapter (which is way more expensive) solves this by deriving power from an USB port...

     

    please explain. thank you!

  • by Grant Bennet-Alder,Apple recommended

    Grant Bennet-Alder Grant Bennet-Alder Feb 5, 2016 5:23 PM in response to mdesignffm
    Level 9 (60,909 points)
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    Feb 5, 2016 5:23 PM in response to mdesignffm

    You have three cases here:

     

    • Non-active adapter asserts a signal back into the Mini DisplayPort interface that forces the Mac port into "compatibility mode". It produces a Single-Link DVI signal, but the signals are at pretty low power levels for DVI signals, but are higher than Mini DisplayPort. You can do this twice before the card can't hack it and the levels drop too low to be useful and one of the three displays drops out.

     

    • "ordinary" ACTIVE adapter also asserts a signal back into the Mini DisplayPort interface that forces it into "compatibility mode". In addition, it contains its own electronics, which boost the low Mini DisplayPort signal levels  up to "real" DVI levels. Its electronics is what commands the US$40 price point. The single power lead in the interface is all that is required, because the signal boosting is done in the adapter. You can attach as many of these as you have graphics output ports for.

     

    • Dual Link ACTIVE Adapters (like the Apple adapter) do not force compatibility mode. They take the entire Mini DisplayPort signal and use a lot of electronics to re-derive a Dual-Link DVI signal, which also contains an additional trio of push-pull drivers to run quite a bit more data, and the power in the Mini DisplayPort power lead is inadequate to run all that Hardware, so they need an additional source of power, and pick that up from the USB pigtail. Its substantial electronics including re-deriveing and adding some data on different outputs is what commands its US$100 price point.

  • by lllaass,

    lllaass lllaass Feb 6, 2016 2:00 AM in response to Grant Bennet-Alder
    Level 10 (188,781 points)
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    Feb 6, 2016 2:00 AM in response to Grant Bennet-Alder

    Grant, that is a very good explanation.

  • by mdesignffm,

    mdesignffm mdesignffm Feb 6, 2016 2:19 AM in response to Grant Bennet-Alder
    Level 2 (306 points)
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    Feb 6, 2016 2:19 AM in response to Grant Bennet-Alder

    thank you, sir! clears things up!

  • by mdesignffm,

    mdesignffm mdesignffm Feb 6, 2016 8:30 AM in response to Grant Bennet-Alder
    Level 2 (306 points)
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    Feb 6, 2016 8:30 AM in response to Grant Bennet-Alder

    sorry, grant, that i ask one more time. short yes-no-question - just to make sure since i have bought some non-working adapters already.

     

    do you think the star tech adapter will work in this setup, finally enabling me to use 3 monitors simultaneously:

     

    monitor 1 (1200 x 1920, DVI) - via passive thunderbolt-DVI-adapter (already mine, working),

    monitor 2 (1200 x 1920, DVI) - via active star tech adapter (to be bought),

    monitor 3 (full HD 1080 x 1920, HDMI) - via HDMI out (working).

     

    what do you think - yes or no?

     

    thank you!

     

    mac pro early 2014

  • by Grant Bennet-Alder,

    Grant Bennet-Alder Grant Bennet-Alder Feb 6, 2016 8:36 AM in response to mdesignffm
    Level 9 (60,909 points)
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    Feb 6, 2016 8:36 AM in response to mdesignffm

    Yes.

     

    you get two "legacy"  passive connections:

    1) monitor 3 built-in HDMI

    2) monitor 1 passive Single-link DVI

     

    then you add the next one through the start tech Single-Link DVI ACTIVE and you are good to go.

  • by lllaass,

    lllaass lllaass Feb 6, 2016 8:36 AM in response to mdesignffm
    Level 10 (188,781 points)
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    Feb 6, 2016 8:36 AM in response to mdesignffm

    What Mac Pro desktop do you have?  The latest is still the late 2013 Mac Pro desktop. Macs are identified when they were released, not sold.

    If you have the late 2013 Mac Pro then what you say should work provided each monitor is connect to a different Thunderbolt bus. That Mac has three TB buses and the HDMI is on a TB bus 0. See:

    Use multiple displays with your Mac Pro (Late 2013) - Apple Support

  • by mdesignffm,

    mdesignffm mdesignffm Feb 6, 2016 8:40 AM in response to Grant Bennet-Alder
    Level 2 (306 points)
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    Feb 6, 2016 8:40 AM in response to Grant Bennet-Alder

    sounds good. i will check where to get the adapter in germany.

     

    thank you!

  • by mdesignffm,

    mdesignffm mdesignffm Feb 6, 2016 8:49 AM in response to lllaass
    Level 2 (306 points)
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    Feb 6, 2016 8:49 AM in response to lllaass

    yes, it is the late 2013. they were delivered here in germany early 2014 only.

     

    thank you for pointing me to allocating the thunderbolt buses. since my post is the unexpected new end to an already long and sad story (i miss my 3rd display!), i am aware of this. nevertheless, i very much appreciate your good point. ;-)

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