Support for native resolution of 3440x1440 on Dell monitor P3421W

I tried your fix but it's not really working on my 2016 13" MBP. As soon as I unplug and plug back in it switches back to 2560x1440. Using displayplacer will then result in a "res not found" error.

Once I reboot I can select the proper resolution again. But only until I unplug again.

Fantastic News - I have found a WORKAROUND!

So my workflow requires that I switch between two MacBooks (1x 2019 MBP and 1x 2016 MBP) frequently. For this reason, the P3421W was a perfect fit with its usb c hub, so I pulled the trigger.

2019 MBP worked like a dream, but my 2016 MBP suffered from the same issue as seen in this discussion.

I failed to believe that outputting 3440x1440@60Hz was beyond the capabilities of the 2016 MBP, most notably because I had seen it do it once or twice after reboots.

After a morning of eye-strain from using the wrong resolution, I was left irritated. I thought "if only there was something xrandr, which would give me more control over the resolution and refresh rate I could set, rather than the MacOS display settings which are irritating at the best of times.

So I had a Google and I found this:

NOTE: In the configuration seen below, I have found that on occasion I get an error where it tells me that the resolution/mode isn't supported. I am able to work around this by simply rebooting, with the usb-c cable connected.

FIX:

https://github.com/jakehilborn/displayplacer claims to be the "xrandr for MacOS", giving you the ability to set the resolution and refresh rate in the CLI.

1. If you have homebrew setup on your machine. you can simply

brew tap jakehilborn/jakehilborn && brew install displayplacer

Or if you don't, just get the built binary from here.

2. execute

displayplacer list

in your terminal. You will get given an output similar to:

Execute the command below to set your screens to the current arrangement:

displayplacer "id:<MY_ID> res:2560x1440 hz:59.9 color_depth:8 scaling:off origin:(0,0) degree:0"

3. copy and paste this output into your terminal, but swap in your values with something like

displayplacer "id:<MY_ID> res:3440x1440 hz:60 color_depth:8 scaling:off origin:(0,0) degree:0"

For the P3421W, we want to ensure we have

res:3440x1440 hz:60

After this, you should see your resolution correct itself... PROFIT!

See attachment for the resolution even showing in the display settings after these steps:

So far I have tested a variety of usb devices alongside these settings and they seem to be working perfectly. Also, the device is charging at a regular speed.

All of this suggests to me that this is either a bug in the hardware of the monitor, but more likely something going on within MacOS.

I would strongly advise that Apple take the necessary action to fix this issue. While this could be seen as a "small bug", I think that it could lead to a lot of infuriated customers as it might seem like Apple are trying to force those 2016 MBP users to upgrade... who said it 😮 

Interesting fix but I notice you posted this to the High Sierra forum and it is quite likely Apple may not do any updates for High Sierra, or possibly at most just security ones, not ones addressing features. This issue may have been released in later macOS releases and for people running hardware that tops out at High Sierra are running hardware that is no longer supported by Apple.

The Macbook Pro 2016 supports Big Sur and I can confirm that this issue is still present on MacOS Big Sur 11.2.3 (20D91).

Sure, the 2016 macbook pro might be 'out of support', but I feel this is something that should be looked at and probably fixed.

If it is an issue with Big Sur then by all means report it to Apple at Apple products feedback links --> http://www.apple.com/feedback/

Sure - The reason I posted was because I knew that OP was experiencing the same issue 😊 Wanted to make sure that they got the fix

HI guys, I was just checking how to fix the same issue and found this.

https://www.youtube.com/watch?v=k2MdxzAC4cA&t=14s

👍