External Dell P2715Q 4K monitor on macOS Sierra?

[milleron]

There are reports of MacBook owners with the Dell P2715Q 4K external monitor losing the ability to scale it to 2560 x 1440 while retaining HiDPI after upgrading to macOS Sierra. https://shrtm.nu/qeSD

I cannot tell if this bug affects macOS Sierra on the iMac (as I don't have enough "reputation points" even to ask a question on that site), and I need to know before upgrading my OS. I don't relish the prospect of finding the bug on the iMac, as well, and then having to roll back the operating system to El Capitan.

Does anyone have an experience to report with this monitor connected via DP or HDMI on an iMac after the upgrade to macOS Sierra?

 

[CheesePuff]

Can not comment on the resolution issue, but I use the Dell P2415Q 4K external via Mini DisplayPort on my rMBP Mid-2014 and it no longer works properly in clamshell mode.

If I restart (such as installing the latest 10.12.1 beta 4 today), the monitor never comes back on and goes into power save mode, then I open the lid on the rMBP and that display remains black, with no fix at all I can find (unplugging/plugging the Mini DisplayPort, hitting every key and key combo imaginable, etc), requiring me to hold down the power button for 7 seconds to force shut down.

Reset the SMC and PRAM a few times, and this is the same behavior on each 10.12.1 beta and 10.12, so its quite annoying.

 

[milleron]

Can not comment on the resolution issue, but I use the Dell P2415Q 4K external via Mini DisplayPort on my rMBP Mid-2014 and it no longer works properly in clamshell mode.

If I restart (such as installing the latest 10.12.1 beta 4 today), the monitor never comes back on and goes into power save mode, then I open the lid on the rMBP and that display remains black, with no fix at all I can find (unplugging/plugging the Mini DisplayPort, hitting every key and key combo imaginable, etc), requiring me to hold down the power button for 7 seconds to force shut down.

Reset the SMC and PRAM a few times, and this is the same behavior on each 10.12.1 beta and 10.12, so its quite annoying.

I'm very sorry to hear that the 10.12.1 beta didn't resolve your problem, because a few users on my previously-referenced thread reported that it did solve their issues. However, their problems were with scaling, rather than total failure of the monitor to display anything