I have two Dell P2715Q 27" external monitors I want to connect to my 15" MacBook Pro 11,3 with OSX 10.10.2 ordered around September 2014. I've tried connecting it as follows:

note: tb = thunderbolt, dp = displayport, mdp = mini displayport

First try

  • tb 1 -> Dell P2715Q #1 dp in -> Dell P2715Q #1 dp out -> Dell P2715Q #2 mdp in

In this case the two Dell screens will only mirror, and OS X does not seem to recognize that there are actually two displays attached.

Second try

  • thunderbolt 1 -> Dell P2715Q #1 displayport in
  • thunderbolt 2 -> Dell P2715Q #2 displayport in

In this case one screen will go on, but the other remains black and says there is no signal.

side note

I also have an older 1920x1200 Dell display I want to use via HDMI for a total of 3 external displays, but I need to get an HDMI cable plus the first two screens working first.

  • maybe see everymac.com/systems/apple/macbook_pro/… I'm not sure really if that's saying they both need to be TB displays. For sure you cannot chain DP displays, only TB
    – Tetsujin
    Commented Feb 22, 2015 at 8:37
  • Did you ever get this working? I'm considering the same setup.
    – ioquatix
    Commented Nov 11, 2015 at 3:57

2 Answers 2


from monitor menu (the buttons) change the MST setting to Primary and Secondary accordingly

  • Ok, I see the MST setting, but how do I wire it and which computer do I set to what? I also found the apple info on 4k displays, which is somewhat useful. support.apple.com/en-us/HT202856 Commented Mar 5, 2015 at 2:51

i'm using DP cable to usb-c on macbook pro m1 - usb-c end - it matters which direction it's plugged into the mac - may have to flip it, even though usb-c goes in both ways

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