I'm at a loss for what to do here, so I'm asking for help! I have a work issued late '13 15" Macbook Pro on 10.9.5 with the discrete GPU and a Dell P2715Q 4k monitor. I should be able to do native 4k or several scaled HiDPI / retina resolutions with this setup - but I can't. OS X and SwitchResX will only allow me to go to 2560x1440 (scaled). On this monitor, thats really blurry and it's hard to code like this. I've tried Googling the issues with no success. I've been playing with SwitchResX all morning and haven't figured it out either. I've created custom resolutions for all of the retina resolutions, but they never active on a reboot - says "invalid" Any pointer on how to proceed here? This is driving me nuts! I have a personal mid-'14 and it has no issues with this display, it works perfectly. Thanks in advance!