@dw0 The display is likely setting up the USB-C link for video and USB 3.x data in order to support the USB ports built into the display simultaneously. When a USB-C link is set up to carry USB 3.x, video bandwidth gets cut in half. The only way to run 3440x1440 with a half-bandwidth link is if the source and display both support DisplayPort 1.3/HBR3 or better, but I don't think that existed for the 2016 15" MBP. It likely only supports DisplayPort 1.2/HBR2 over USB-C. In that case, the only way to run 3440x1440 60 Hz over USB-C would be to limit USB data speeds to USB 2.0, which allows a full-bandwidth video link. Some Dell displays have a USB-C Prioritization option in their onscreen interfaces to allow you to choose between these modes, but I'm not sure about that particular display. (EDIT: It seems that 3440x1440 and USB 3.x may be possible simultaneously even with an HBR2 system, at least from a pure bandwidth requirements perspective.)
As for HDMI, the likely reason you're limited to 30 Hz there is because 3440x1440 60 Hz would require HDMI 2.0, which I'm pretty sure didn't exist in 2016 either.
If you can't configure the display to set up the link for full video bandwidth and USB 2.0, the only way you'd likely get full resolution and refresh rate is with a USB-C to DisplayPort cable, which will force the link to run at full video bandwidth since it won't carry USB data at all. But then you'd have to run a separate cable for USB 3.x data if you wanted to use it, and you'd no longer be able to draw power from the display. At that point the only way to get power, USB 3.x data, and enough video bandwidth to run your display properly would be a Thunderbolt 3 dock of some kind, but that's of course more cost and complexity.
So hopefully there's an option somewhere in the display's interface along the lines I described.
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.
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: 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
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. We can see that the P3421W driver page ONLY offers Windows operating system drivers.
@dw0 Adding a bit to my reply above, here is an adapter that may provide a sufficient solution for your purposes. If you got this, then you could connect a DP cable from the adapter to the display and the USB-C cable from the display's USB-C input to the USB-C power passthrough port on the adapter. Then you'd have video and power coming into your system on a single cable. And then if you also got a USB-B to USB-C 3.0 cable like this one, you could connect the upstream USB 3.0 port of the display to a separate USB-C port on your MacBook and you should be good to go. That's about the best you'll be able to do since again if I'm correct that your 2016 MBP 15" only supports DP 1.2/HBR2 over USB-C, there's no way to run 3440x1440 60 Hz and USB 3.x data simultaneously over a single cable except by relying on Thunderbolt 3, which the display doesn't support.
Lastly, be aware that the U3421W only supports up to 65W of power over USB-C, whereas I believe the 15" MBP is designed for 87W. It will still work from a 65W source, but you may see slower battery charging and/or reduced performance in some situations if you decide to use the display as your power source.
Thanks for the fast answer @jphughan -- and on a Sunday no less!
I think you're right on all accounts here. Unfortunately my monitor doesn't have a "USB-C Prioritization" option, so I'm stuck using the DisplayPort if I want to use anything > 30Hz at full resolution. My PC is currently using the DisplayPort input and also doesn't have HDMI 2.0, so I'll probably just suffer @ 30Hz via HDMI until I can upgrade my video card on the desktop or something.
@dw0 Happy to help! Sorry I didn't have a better answer for you though. One option that may work in your case would be a USB-C to HDMI 2.0 adapter/cable. I tend to recommend USB-C to DP whenever there's a choice because USB-C uses DisplayPort natively, so that's basically a simple passthrough adapter, whereas USB-C to HDMI 2.0 adapters/cables have to incorporate an active signal converter chip, and those seem prone to occasional interoperability issues where a laptop might work fine with one brand of that adapter but not another one. But if your display's DP input is occupied, that adapter might allow you to run its HDMI 2.0 input from a source on your system that can actually push 3440x1440 60 Hz. Good luck!
You know what, I think I noticed that behavior once. The login screen after rebooting was at the right resolution but then when I logged in it went back to the poorly-scaled one. I'll have to try it again, thanks for the tip.
Also, I'm not sure that the solution described earlier in this thread is correct. I think USB-C can carry 3440x1400@60Hz (over displayport 1.2) and USB 3 speeds at the same time.
I have this exact problem with a 2016 Macbook 12". It works fine at 3440x1440 if I reboot the Macbook while it's connected to the monitor - does this work for you?
@ip75 Your post motivated me to check some math. Ultrawide resolutions are seldom accounted for in specs since they're a minority of the display population, and that's especially true in the specs of docks that are primarily business-oriented products where ultrawides are even less commonly found. So here's what I've found:
A 2560x1440 60 Hz display requires about 5.6 Gbps of effective bandwidth, i.e. not counting overhead.
A 3440x1440 display has 34.3% more pixel area, so using the same refresh rate, it would require about 34.3% more bandwidth, which would be about 7.5 Gbps of effective bandwidth.
Two lanes of DisplayPort HBR2 gives you 8.6 Gbps of effective bandwidth.
So from a pure bandwidth requirements standpoint, it seems you are correct. I've updated my earlier post to reflect this. Thank you for calling this out. And based on this, I'm not sure what the problem is in the original setup discussed here.
Good find @djw0bbl3 , I wasn't successful though The 3440x1440 resolutions weren't listed after running `displayplacer list` and I got the following error when trying to set it:
Screen ID $ID: could not find res:3440x1440x60 color_depth:8 scaling:off
I'm having the same problem with my 2016 13" MacBook Pro. Everytime I unplug it and plug it in again it sets a max of 2560x1440. Rebooting then lets me select the proper 3440x1440 until I unplug it again.
I am under the suspicion that MacOS doesn't properly detect the monitor when connected from sleep mode but only on boot.
jphughan
9 Legend
•
14K Posts
1
February 28th, 2021 09:00
@dw0 The display is likely setting up the USB-C link for video and USB 3.x data in order to support the USB ports built into the display simultaneously. When a USB-C link is set up to carry USB 3.x, video bandwidth gets cut in half. The only way to run 3440x1440 with a half-bandwidth link is if the source and display both support DisplayPort 1.3/HBR3 or better, but I don't think that existed for the 2016 15" MBP. It likely only supports DisplayPort 1.2/HBR2 over USB-C. In that case, the only way to run 3440x1440 60 Hz over USB-C would be to limit USB data speeds to USB 2.0, which allows a full-bandwidth video link. Some Dell displays have a USB-C Prioritization option in their onscreen interfaces to allow you to choose between these modes, but I'm not sure about that particular display. (EDIT: It seems that 3440x1440 and USB 3.x may be possible simultaneously even with an HBR2 system, at least from a pure bandwidth requirements perspective.)
As for HDMI, the likely reason you're limited to 30 Hz there is because 3440x1440 60 Hz would require HDMI 2.0, which I'm pretty sure didn't exist in 2016 either.
If you can't configure the display to set up the link for full video bandwidth and USB 2.0, the only way you'd likely get full resolution and refresh rate is with a USB-C to DisplayPort cable, which will force the link to run at full video bandwidth since it won't carry USB data at all. But then you'd have to run a separate cable for USB 3.x data if you wanted to use it, and you'd no longer be able to draw power from the display. At that point the only way to get power, USB 3.x data, and enough video bandwidth to run your display properly would be a Thunderbolt 3 dock of some kind, but that's of course more cost and complexity.
So hopefully there's an option somewhere in the display's interface along the lines I described.
djw0bbl3
2 Posts
0
March 22nd, 2021 08:00
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
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:
3. copy and paste this output into your terminal, but swap in your values with something like
For the P3421W, we want to ensure we have
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. We can see that the P3421W driver page ONLY offers Windows operating system drivers.
jphughan
9 Legend
•
14K Posts
1
February 28th, 2021 09:00
@dw0 Adding a bit to my reply above, here is an adapter that may provide a sufficient solution for your purposes. If you got this, then you could connect a DP cable from the adapter to the display and the USB-C cable from the display's USB-C input to the USB-C power passthrough port on the adapter. Then you'd have video and power coming into your system on a single cable. And then if you also got a USB-B to USB-C 3.0 cable like this one, you could connect the upstream USB 3.0 port of the display to a separate USB-C port on your MacBook and you should be good to go. That's about the best you'll be able to do since again if I'm correct that your 2016 MBP 15" only supports DP 1.2/HBR2 over USB-C, there's no way to run 3440x1440 60 Hz and USB 3.x data simultaneously over a single cable except by relying on Thunderbolt 3, which the display doesn't support.
Lastly, be aware that the U3421W only supports up to 65W of power over USB-C, whereas I believe the 15" MBP is designed for 87W. It will still work from a 65W source, but you may see slower battery charging and/or reduced performance in some situations if you decide to use the display as your power source.
dw0
7 Posts
0
February 28th, 2021 10:00
Thanks for the fast answer @jphughan -- and on a Sunday no less!
I think you're right on all accounts here. Unfortunately my monitor doesn't have a "USB-C Prioritization" option, so I'm stuck using the DisplayPort if I want to use anything > 30Hz at full resolution. My PC is currently using the DisplayPort input and also doesn't have HDMI 2.0, so I'll probably just suffer @ 30Hz via HDMI until I can upgrade my video card on the desktop or something.
jphughan
9 Legend
•
14K Posts
0
March 1st, 2021 07:00
@dw0 Happy to help! Sorry I didn't have a better answer for you though. One option that may work in your case would be a USB-C to HDMI 2.0 adapter/cable. I tend to recommend USB-C to DP whenever there's a choice because USB-C uses DisplayPort natively, so that's basically a simple passthrough adapter, whereas USB-C to HDMI 2.0 adapters/cables have to incorporate an active signal converter chip, and those seem prone to occasional interoperability issues where a laptop might work fine with one brand of that adapter but not another one. But if your display's DP input is occupied, that adapter might allow you to run its HDMI 2.0 input from a source on your system that can actually push 3440x1440 60 Hz. Good luck!
dw0
7 Posts
0
March 3rd, 2021 07:00
You know what, I think I noticed that behavior once. The login screen after rebooting was at the right resolution but then when I logged in it went back to the poorly-scaled one. I'll have to try it again, thanks for the tip.
ip75
1 Rookie
•
12 Posts
0
March 3rd, 2021 07:00
Also, I'm not sure that the solution described earlier in this thread is correct. I think USB-C can carry 3440x1400@60Hz (over displayport 1.2) and USB 3 speeds at the same time.
ip75
1 Rookie
•
12 Posts
1
March 3rd, 2021 07:00
I have this exact problem with a 2016 Macbook 12". It works fine at 3440x1440 if I reboot the Macbook while it's connected to the monitor - does this work for you?
jphughan
9 Legend
•
14K Posts
0
March 3rd, 2021 08:00
@ip75 Your post motivated me to check some math. Ultrawide resolutions are seldom accounted for in specs since they're a minority of the display population, and that's especially true in the specs of docks that are primarily business-oriented products where ultrawides are even less commonly found. So here's what I've found:
So from a pure bandwidth requirements standpoint, it seems you are correct. I've updated my earlier post to reflect this. Thank you for calling this out. And based on this, I'm not sure what the problem is in the original setup discussed here.
dw0
7 Posts
0
March 22nd, 2021 08:00
Good find @djw0bbl3 , I wasn't successful though The 3440x1440 resolutions weren't listed after running `displayplacer list` and I got the following error when trying to set it:
Screen ID $ID: could not find res:3440x1440x60 color_depth:8 scaling:off
I'm glad you got yours working at least.
dw0
7 Posts
1
March 22nd, 2021 10:00
Oh snap it worked... Thank you! \m/
Definitely something Dell/Apple should get sorted out since it definitely is possible with this workaround.
djw0bbl3
2 Posts
1
March 22nd, 2021 10:00
Don't worry, I got the same at first! I would:
DELL-Cares
Moderator
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27.6K Posts
0
March 22nd, 2021 11:00
Hi,
I have replied to you from a private message.
-Gautam.
dw0
7 Posts
0
March 22nd, 2021 11:00
@djw0bbl3 My success was short-lived... it looks like I have to do this after every time my Macbook goes to sleep. Are you having the same issue?
MintyHulk
1 Message
0
April 3rd, 2021 03:00
I'm having the same problem with my 2016 13" MacBook Pro. Everytime I unplug it and plug it in again it sets a max of 2560x1440. Rebooting then lets me select the proper 3440x1440 until I unplug it again.
I am under the suspicion that MacOS doesn't properly detect the monitor when connected from sleep mode but only on boot.