robhayden

Q: Cannot run two monitors (Dell U3415W)

Computer:Mac Pro (Late 2013)
Graphics:AMD FirePro D300 2048 MB
OS Version:OS X Yosemite 10.10.1
Monitors:2x Dell U3415W
Monitor 1 via HDMI
Monitor 2 via Thunderbolt to DisplayPort on connection port #2

 

 

I am having a problem getting two of my monitors to work properly on my Mac Pro.  When powering on the machine, only monitor #1 works.  When going to the system information (About This Mac/Display), my system recognizes both monitors.  It is able to pull the model number, serial number, resolution and such for both monitors, so I know there is good communication.

 

 

When looking at the display options and trying to do a shared/extended view, monitor #2 does not display an image.  In fact, the monitor goes into sleep mode.  When I choose mirror mode, I get the same result.  Here is where it gets odd.  If I modify the frequency of monitor #2 to 50hz (PAL), it works!  However, when I switch back to extended mode, monitor #2 goes back to black.  In extended mode, I've tried switching between 30hz and 50hz, and nothing works.

 

 

I have tried several other combinations to rule out monitor related issues, cable issues, etc.

- HDMI on monitor #2, DisplayPort on monitor #1 - issue follows DisplayPort

- Use the Apple Thunderbolt to Thunderbolt wire to connect to the Mini DisplayPort on both monitors simultaneously

- Tried all Thunderbolt connection ports on the back of the MacPro

- Use different HDMI and DisplayPort cables

- Rebooted computer every time after each change

 

 

Any idea how I can resolve this issue?  I find it strange that I can get everything to work in mirror mode if monitor #2 is at 50hz (PAL), but that's it.  In that small test case, it shows to me that the Mac Pro is able to communicate with both monitors, display a clear imagine, that both monitors function properly, including all cables and connection ports.  It leads me to believe it is an OS configuration issue.

 

 

Thank you.

Mac Pro, OS X Yosemite (10.10.1)

Posted on Jan 21, 2015 5:18 PM

Close

Q: Cannot run two monitors (Dell U3415W)

  • All replies
  • Helpful answers