I have had an issue with my new(old) 2013 mac pro and dual screens. I have the thunderbolt connections as recommended from the apple manual. Please see the screen shots for secondary monitor equipment that i have installed. The primary monitor is the 27" thunderbolt. The ongoing issues that I have are the following: 1) Garbled screen as shown in the photo on reboot. 2) Once it boots up with a garbled screen, and I recover by logging in via screen sharing. I can fix the issue by changing the resolution on the MAIN screen. Once changed, the computer will crash with an error once it goes to sleep. The only way it does't crash? I have to successfully reboot without a garbled screen. 3) I can go for a month without problems (maybe from not rebooting). But as long as i can reboot without a messed up screen i'm good to go for a while. 4) Once I have a successful boot with the primary monitor, as long as I keep the 2nd monitor off then everything works pretty well. My simple Conclusion: It's the 2nd monitor or a fault in the mac pro D700's.