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 1920×1200 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.
Best Answer
from monitor menu (the buttons) change the MST setting to Primary and Secondary accordingly