I have a Mid-2014 15" Macbook Pro w/ Intel Iris graphics running El Capitan 10.11.2. With my old 1080p monitor attached via a Mini DisplayPort to DVI cable, the screen saver and display sleep options (in System Preferences -> Energy Saver) work as expected. However when I replace the monitor with a Dell P2715Q 4k monitor attached via a Mini DisplayPort to DisplayPort cable, the monitor stays on forever and both the screen saver and display sleep options never activate. I can manually put the display to sleep via the keyboard shortcut Control-Shift-Eject. I have tried with both the monitor being detected as "Television: Yes" and with the Force RGB mode patch. Any ideas on how to resolve this?