MacBook Pro 11,3 with dual Dell P2715Q 27" Monitors 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.
from monitor menu (the buttons) change the MST setting to Primary and Secondary accordingly