Got a MVC flashed GeForce 750 Ti in my 4,1 and so far I'm very happy. Now I can keep my 4K monitor on/in DP1.2 mode and be able to successfully boot and see the boot screen. However, an issue remains that I also experienced with my previous 7950 setup--OS X assumes my setup isn't HiDPI capable. I go into Display Preferences and instead of seeing the slider of HiDPI options I see the old-style list of resolutions (none of which are HiDPI). I bought the helper app "Display Menu" which does allow me to set HiDPI resolutions. I've bookmarked a few favorites. But every time I reboot, the resolution resets to 3840x2160 and I have to manually change back to the HiDPI res. This is in contrast to my rMBP which does remember my HiDPI resolution choice and maintains it through reboots. So my guess is that the two issues are related. My questions to the gurus here: 1. Is there any way to tell OS X on my cMP that the machine is HiDPI capable and to offer up the HiDPI GUI elements in Display Preferences? 2. If solving #1 doesn't also fix the problem of reverting to 3840x2160 after each reboot, are there any other solutions to that? Apologies if this is covered in other threads. I did search a bit but didn't find a whole lot pertaining to this exact issue. Edit: I should add that I'm running 10.11.4. Haven't tried to see if behavior is any different under Yosemite.