Dell UP2715K on M1 Machines - 5K @60hz Possible?

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Level 1

9 points

Dell UP2715K on M1 Machines - 5K @60hz Possible?

I've been using my Dell UP2715K monitor for years across many Apple laptops. In order to hook it up to all of my laptops that support Thunderbolt 3, I have used the following dongle with no issue: https://www.startech.com/en-us/audio-video-products/tb32dp2t - it takes two DisplayPort cables that hook up to the display, and then just one Thunderbolt 3 cable goes into the Mac*(For why see the bottom of the post). I am using it right now on Big Sur 11.0.1 on my 2018 15" MacBook Pro with discrete graphics. It supports 5K at 60Hz just fine. It also works on my wife's 2019 13" MacBook Pro with integrated graphics as well as a 2019 MacBook Air with integrated graphics. Both of these machines also support this laptop with the same adapter just fine.

I ordered a M1 Apple Silicon MacBook Air recently since it said it support 1 monitor of up to 6K up to 60Hzto my surprise. Surely, my 5K monitor should work? Unfortunately I haven't had luck yet. The display shows up in "About This Mac" as recognized by macOS, but the monitor does not recognize a signal being sent. Also, the resolution listed in "About This Mac" is not the full resolution - it's 800x400 or something along those lines. Has anyone been able to get this combo to work on their end?

*Why this monitor needs two cables to do 5K and the crazy adapter I linked above: It was one of the first 5K displays available, and was featured in Apple's keynote when they announced support for 5K monitors. It is a strange beast that requires two full-size DisplayPort cables to get a 5K 60hz signal. It does this using Displayport MST (Multi-Stream Transport) where DisplayPort combines two DisplayPort streams into one to support one 5K 60Hz signal. At the time it was released, neither DisplayPort of HDMI support enough bandwidth to drive the display.

MacBook Air 13″, macOS 10.15

Posted on Nov 22, 2020 9:24 PM

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Answer 1

Alex Argo Author

Level 1

9 points

Nov 29, 2020 11:37 PM in response to Wheelie80

So I've had multiple calls with Apple and I think I'm pretty close to having my monitor working properly with the dongle I mentioned above. The trick that I didn't realize at first was that even though only 848x600 resolution was listed by the display under preferences, I could click "Gather Windows" to get the Display window to come onto my MacBook Air display. This let me option click 5120x2880. At this point, the display was working in 60Hz at full resolution, but I couldn't use clamshell mode. The only issue is that it was not scaled properly. (ie everything was very small. I really wanted a "looks like" display of 2560x1440 running at 5120x2880. I downloaded SwitchResX and got that working after much tweaking and can now use clamshell mode. The Apple Support specialist I have been speaking with is supposed to call me back Tuesday with a workaround that won't require SwitchResX that should enable all of the same things hopefully. Unfortunately, things are not "just working", but I have gotten them to work for now. This monitor has always been a unique snowflake. I'll post with any updates.

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Answer 2

Alex Argo Author

Level 1

9 points

Dec 28, 2020 10:26 PM in response to Wheelie80

Good news and bad news, but mostly good news:

Bad news: macOS 11.1 didn't seem to fix things by itself. I was hoping Apple would add in support for this monitor but hasn't.

Good news: I spent a lot of time on the phone with Apple support gathering info and with them trying to troubleshoot and at the end of the day, their workaround ended up being to be exactly what SwitchResX was doing: Generate a display overrides file to fix things. I ended up just using SwitchResX in demo mode to generate one that worked for my needs. I believe I just enabled the default and scaled resolutions for the monitor which enables clamshell mode. It seems to be working well with 5k resolution at 60Hz. I've been running it as my daily driver for a month or so. If you want the other scaled resolutions, you might have to fiddle with SwitchResX some more. After generating the plist file with SwitchResX, I was able to uninstall SwitchResX and just leave the plist file it generated there and everything worked the same. One odd thing I noticed was when I open the M1 MacBook Air for some reason, I lose the 2x scaled mode. This does not happen when I run it in clamshell mode. I'm guessing I could figure out why this was and fix it with SwitchResX, but I haven't messed with it.

The file SwitchResX generates lives at /Library/Contents/Overrides/DisplayVendorID-90ac/DisplayProductID-40b6, so it's applied to all users, works on the login screen/etc. I would post the contents here, but you should probably at least give the SwitchResX demo a shot: https://www.madrau.com

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Answer 3

Nov 23, 2020 10:16 AM in response to Alex Argo

I have the same display and my purchase of the M1 MacBook Air pretty much depends on if I can still use it without any restrictions or not.

Did you try hard resetting the UP2715K?

Factory reset the monitor (menu -> Others -> Factory Reset)
Turn the monitor off
Disconnect every cable (including the power cable) from the monitor
Press the power button for 8 seconds
Reconnect ONLY the power cable to the monitor and turn it on
Connect the DP cables and test

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Answer 4

Bobshop

Level 1

4 points

Jan 6, 2021 4:34 AM in response to Alex Argo

Hello Alex,

Thanks for the useful information. I have a similar problem with an OWC 2x DP monitor (looks like exactly what you have but with a different branding) and the same monitor.

I can get a 5k image but without the scaling so the text is small. I needed to install SwitchResX to do this. Sometimes if I close the laptop (MacBook Air M1) and reopen the scaling works and I get the effective 2560x1440 resolution.

Are you able to describe exactly what you did to generate the plist file etc?

From looking at the SwitchResX site the custom resolution function (e.g. for HiDPI displays) is not yet available for Apple silicon.

Annoying to have to have a slightly janky solution but these monitors are delicate flowers and maybe there will be an OS update that fixes things.

Thanks in advance!

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Answer 5

Jan 13, 2021 4:42 AM in response to Bobshop

Happy to report my UP2715k works on my new MacBook Air M1 as well via the TB32DP2T. Behaviour is exactly as you described, Alex. I launched SwitchResX once, switching from dual screen to clamshell mode is seamless now. I've turned off the MacOS screen sleep setting when running on the power adapter and did the same in the Dell's energy settings.

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Answer 6

Nov 24, 2020 11:44 PM in response to Alex Argo

In the meantime I'm pretty sure the solution is a DisplayLink-enabled adapter, e.g. Startech's DK30C2DPEP. DisplayLink adapters have been shown to allow using up to 6 displays on a MacBook Air M1.

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Answer 7

Alex Argo Author

Level 1

9 points

Nov 29, 2020 11:29 PM in response to Wheelie80

The display factory reset didn't seem to help at all.

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Answer 8

Nov 30, 2020 1:19 AM in response to Alex Argo

Awesome to hear the adapter is working in principle! So I can place my order for the adapter and the M1 Air now :) Yep, I guess there's a reason why it got taken off the market so fast.

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Answer 9

Dec 11, 2020 5:37 AM in response to Alex Argo

Hello Alex, what's your experience been for the past 2 weeks with the M1 MacBook Air + TB32DP2T + UP2715K combo? Could you get rid of using SwitchResX? 5K@60Hz working reliably in clamshell mode?

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