Multiple Displays have problems with El Capitan

I upgraded to El Capitan last week. Immediately after restarting from the install, my 2nd and 3rd monitors no longer displayed anything. It's like they were turned off. I tried restarting, but nothing changed. I then tried switching cables to different ports and seeing what would happen with just a single monitor plugged in, here's what I found.

Machine Info:



AMD FirePro D500 3072 MB Graphics

27" Apple Cinema Display (x2) using Thunderbolt

13HD Wacom Cintiq using HDMI


When 1 monitor was plugged in, it would work fine.

When 2 were plugged in, only the first monitor would work

It seems that changing ports made no difference, only 1 monitor would work at any given time. I also had issues with some external drives failing to mount.

I called AppleCare and they had me reset the SMC on the MacPro. This seemed to fix it until I setup my second cinema display with Apple Calendar and Apple Mail in the new split view and quit the applications without exiting SplitView first. Doing this blacked out the second Cinema display and I had to repeat the SMC reset procedure (listed below). It happened again about an hour later after a restart, I called AppleCare again and the tech led me through the SMC reset steps again and all monitors began working properly again. Within the next few hours the same problem happened again...I am now back on Yosemite until I see something indicating this problem is fixed.

I noticed that Beta users had this problem documented quite a bit on the .3 release, but I saw that the .4 release seemed to fix the issue. Well, it did not. I caught lightening in a bottle and it's happening to me.

SMC Reset Procedure

1. Shut Down computer if it's not already shut down

2. Unplug all peripherals and computer for 30 seconds

3. Plug in computer to power and one monitor

4. Start-up and check to see if monitor is working

5. If monitor is working then plug-in second display and restart

This worked for me and I was able to plug up the other peripherals.

I'm not sure why the problem persists, but everything is completely stable and operates fine on Yosemite.

Has invited:

howapple - hello

Favor from:

Rdruhl wrote:

That is interesting that you have to use the Option key. Why did they not just make another button? And how did you know that you had to use the Option key? Anyway, I tried it, and I still do not get the Menu or Dock on the second display.

Try System Preferences->Mission Control

It appears that the setting for "Displays have separate Spaces" was lost. You need to have that box CHECKED in order to have menu bars (and the dock, if it is set to appear at the bottom) on every display.

You need to log out and log back in for this change to take effect.

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