After the 10.9.3 update the new Mac Pro will only recognize two monitors. Any two but only two.
I have not change the arrangement of the ports either. I have the two 30″ displays plugged into (1) the upper left TB port and the other (2) is in the upper right TB port. This puts them on separate buses. The HDMI port has nothing plugged into it (this includes the bottom two TB ports on the same bus as the HDMI port) except an HD monitor.
The Displays preference pane will only see two monitors after the OS 10.9.3 update.
All fine here with my rMBP. Had to use alt-key in display prefs for my HP Dreamcolor to change the res back to 1080p to use it as my third monitor and full screen output for FCP X through the HDMI port.
Jari, I suspect that the update doesn’t like the 30″ monitors I’m running even though they are connected using an active adaptor. But it worked before the update. Please know that I’m not saying the update won’t run three monitors. I’m just saying it won’t run my set of three monitors.
I, too, can confirm this issue with a new Mac Pro with dual D500 video (doubt that matters though).
As soon as I upgraded to OS X 10.9.3, I lost my third display. I’m using 3 identical 27″ LG monitors running at 1920×1080 resolution. One connected directly via the HDMI port on the Mac Pro, one via a Mini-DP to HDMI passive dongle/adapter, and the third via Apple’s $99 Dual link DVI to Mini-DP adapter.
This especially irritates me because I never ran more than 2 displays before, until I invested in this new Mac Pro. That’s when I decided I may as well splurge with it and get a third matching display screen, and a triple monitor VESA mounting bracket to put them on. That’s when I discovered the nMP had the limitation of requiring one of your connections to be active vs. passive if you want more than 2 displays, so I went out and spent the $99 on the dual-link DVI to Mini DP contraption. Now, only a few weeks after getting that all going — I’m back to 2 monitors again anyway!
I did file a bug report with Apple, BTW. We’ll see how quickly this gets fixed ….
Mavericks 10.9.3 has also affected dual display on my early 2009 Mac Pro. At first only one monitor responded. The menu bar was greyed out and I couldn’t move the cursor across the two displays. I went into System Prefs and tried dragging displays, gathering displays, mirroring all to no avail. I then restarted, tried it again and it appears to be working now. However, Monitor # 1 is on the left and # 2 on the right. I can’t seem to swap them. For some strange reason I had set # 1 on the right and #2 on the left.
I just finished working on a project last night. At first glance, FCP X appears quicker, more responsive after upgrading to Mavericks 10.9.3.