Hey,
I’m thinking about getting an iMac Pro and I’m hoping that I can continue to use my Dell 2715K display as a second screen, but I cannot find a definitive answer on whether it’ll work. I asked Apple Support about it and they linked me to this:
http://apple.co/1OygOoT
I found this part in the article and asked them about it:
“The Dell UP2715K 27-inch 5K display is supported by iMac (Retina 5K, 27-inch, Late 2014) and later and Mac Pro (Late 2013) running OS X Yosemite v10.10.3 and later.”
Does that include the iMac Pro or does it mean only iMac (sans Pro) with a 5K Display are supported for this external monitor?
They replied that it was a good question and that I should ask Dell about it. Why, I do not know. They have not reacted to any more follow-up questions. Dell have not gotten back to me yet.
Does anyone have this exact setup? Does it work?
Yes, the Dell UP1715K will work. I've got two of them plugged into my iMac Pro right now. I'm typing this on one. I used to have one of them plugged into a late-2015 27" iMac.
A few caveats though...
1) If you have Thunderbolt 3, you'll need a TB3 to dual-DisplayPort adapter. I use ones from Sonnet. MAKE SURE that you get the one that's specifically advertised as being MacOS compatible. The PC versions are a little bit cheaper, but aren't certified with Apple as approved TB3/USB-C devices. The hardware is exactly the same, but Macs won't connect to uncertified TB3/USB-C devices.
If your Mac has dual TB2 ports (like my old iMac did), then you'll just need Thunderbolt 2 to DisplayPort cables. My Dells came with these, but since you'll have to buy them used, you may not get them included.
2) If you have an old version of MacOS, you may have to edit your PRAM variables to enable monitor spanning before 5K mode will work.
3) Get a monitor resolution-switching app like "Display Menu" (it's in the App Store), since the Mac won't properly auto-detect the resolution of the monitor. By default it probably will not display in "Retina" mode, and all of your menus and text will be teeny-tiny until you enable retina-mode with Display Menu.
4) If you're connecting multiple 5K monitors to an iMac Pro, make sure you use only even or odd USB-C ports. Like #1 and #3, or #2 and #4. That's because the first two, and last two USB-C ports use different "lanes" or something. One lane/controller/whatever can't handle the data load for two 5K monitors at once. This is why newer iMacs with 2 TB3/USB-C ports can't connect more than one 5K display.
5) You'll have to fiddle a bit with the port connections, because the Dells are combining two different data streams into one 5K picture. One port carries a 4K signal, and the other carries the rest. Get them out of order and your monitor will show up as two different monitors with crazy stretched images.
6) Set the color profiles for all of your monitors to "Adobe RGB (1998)" and they'll match way more closely than if you try and color-calibrate them yourself.
7) Expect a few glitches. These Dells black-screen for 4-5 seconds whenever you change resolutions or switch inputs. One of my Dells does this every hour or so on its own while I'm working. Never happened on the 2015 iMac, and its frequency has gone down with every update, so I'm blaming MacOS on this one.
Good luck. It sucks that these old out-of-production Dells look and operate much better than the LG 5K display Apple is selling. I have one of those too, for my laptop, and I hate it with a passion. Power button? Who needs a power button on a $1500 display? No, you're supposed to plug in your sleeping laptop for a charge, and then log in to be able to put it back to sleep (facepalm).
