Mba 2015 with Dell U2515H + Imac 27 mid2010

Discussion in 'MacBook Air' started by frogmds, Jan 12, 2016.

  1. frogmds macrumors newbie

    frogmds

    Joined:
    Jan 12, 2016
    #1
    Hi all!

    This Christmas, I have given a Macbook 2015, previously my setup was an iMac and Dell U2515H monitor as the secondary monitor.

    I've been reading about how to have 2 screens connected to the MBA using the MST port (daisy chain) from dell monitor (daisy chain).

    Once connected all devices, I've got mirror image from the secondary monitor on the iMac when the target active mode (cmd + f2).
    The macbook does not detect a third screen, only two screens, mba and dell.

    If I connect macbook to imac, the imac is detected as secondary monitor, without using the target mode (cmd + f2)


    This is the configuration:

    Macbook Air (mini Displayport) -> Dell Monitor (Displayport)
    Dell monitor (MST Displayport) -> Imac (mini Displayport)


    Can anyone give me a clue about why this happens?

    - The imac is the problem? With another monitor will works?
    - I Use a standar mini displayport cable from the MacBook Air to Dell. Need a Thunderbolt cable?
    - Will i need other quality cables? Active clabes maybe?

    Thanks!
     
  2. JTToft, Jan 19, 2016
    Last edited: Jan 19, 2016

    JTToft macrumors 68040

    Joined:
    Apr 27, 2010
    Location:
    Aarhus, Denmark
    #2
    Interesting setup. As yet, I can't remember anyone getting DP 1.2 MST working with extended screens in OS X - unfortunately. This thread seems to point to it indeed being the case that OS X doesn't support it.
    But you should still at least see mirrored screens across all three devices. Unless there's some limitation that doesn't allow the iMac to participate in such a daisy chain (which could easily be the case).

    You definitely don't need any Thunderbolt cables, as neither the Dell nor the iMac can use that.

    A few obvious questions: Are you sure all your DisplayPort cables are 1.2? Have you enabled DP 1.2 in the monitor's menu? Are you sure you are connecting the cables properly to the DP in and DP out on the monitor (they are not interchangeable)?

    If all's well with those questions, I'm betting DP daisy chaining just doesn't work with an iMac. It could be the case that the iMac's Target Display Mode can't "see" the attached MacBook Air through the Dell and so doesn't know it's getting an input.
     
  3. frogmds thread starter macrumors newbie

    frogmds

    Joined:
    Jan 12, 2016
    #3
    Hi!

    I dont know if my cables are 1.2 or not, i tried to find how identificate 1.2 or 1.1 cables and nothing clear.
    In this link i http://www.displayport.org/cables/how-to-choose-a-displayport-cable-and-not-get-a-bad-one/ writes about it
    "Despite what you may read, there is no such thing as a DisplayPort 1.1 cable and DisplayPort 1.2 cable."

    Yes, on my Dell is 1.2 MTS activated

    Only mirror image at the moment, the same picture of Dell is on Imac.

    I will try on Windows and without imac, a Lg and Asus (to hdmi)

    Thanks!
     
  4. JTToft macrumors 68040

    Joined:
    Apr 27, 2010
    Location:
    Aarhus, Denmark
    #4
    - Interesting. I'll have to check out that cable thing a bit further.

    Oh, so you do actually get a picture across all three screens with the MBA as the source? But only a mirrored picture?
    If so, that would support the theory that OS X doesn't properly support DP 1.2 daisy-chaining. All should work if you boot into Windows.
     
  5. frogmds thread starter macrumors newbie

    frogmds

    Joined:
    Jan 12, 2016
    #5
    Here is a screens.

    On Win10 (bootcamp) is perfect with 3 screens.
    [​IMG]


    On Osx only 2 :_(
    [​IMG]


    Yeah, the problem is OSX. Maybe in 10.12...

    Thanks for all.
     
  6. JTToft macrumors 68040

    Joined:
    Apr 27, 2010
    Location:
    Aarhus, Denmark
    #6
    Thanks for confirming.

    It really sucks that OS X doesn't support it. I, myself, have a different project I'd like to do: Mirrored screens using my pre-DP1.2 MacBook Pro.
    I'd like to have a daisy chain out from the U2515H to my TV via DP to HDMI cable. I have no use for extended for this scenario as it's just for use on the rare occasion I need an actual cable between my machine and the TV. Would make it far easier to just have one attached permanently in this way.
    I have seen someone confirm getting mirrored screens using a DP1.1 machine and DP daisy chaining. But I couldn't get it to work with the cable I got. I figured it was because it was a DP1.1 cable, but your displayport.org link would seem to contradict that.

    If you have any suggestions...
     

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