U4021QW, MacBook Pro M1 Pro, connection dropping

Question

Hello everyone,

Just got my new Dell U4021QW - an amazing monitor!

I have done the following:

1. Updated the firmware to the latest one, M2T104.

2. Install the latest DDPM on both Windows and Mac.

KVM switch with one key working great on both windows and macOS.

Now for the issues - which are only on the Mac:

1. Connecting with TB3 from the monitor directly to Mac keep disconnecting, after up to 1m the connection drop then get back again. Sometimes there isn't any connection I need to unplug the cord from the monitor or turn it off to get the connection back on (not sure if both are really needed).

Currently to make the connection stable I'm using my CalDigit Ts3 Plus, connected from the TB3 on the monitor directly to the TB3 on the CalDigit and then to the TB connection on the Mac.

Obviously I was hoping to not use the dongle.

2. The split screen option in DDPM is working only in windows, in Mac I am getting an error about write permission...

My MacOS version is: 12.3

Thanks!

ngolden · Answer

I found a better workaround for the big issue - if you change the DP mode to 1.2 on the TB3 connector everything is working fine, with no connection drop at all.

I did notice that on my desktop connected with DP to Nvidia GeForce GTX 1060, the color depth is 24bit, while with the TB3 using DP1.4 is 30bit - when changing the TB3 to DP1.2 the color depth is 24bit as well.

Maybe it will help Dell devs to fix this issue in a firmware update.

Issue 2 is still in hand, I'm using Rectangle app instead, the DDPM is used only for the KVM shortcut switch (which works great).

Note I'm using Dell own provided cables for everything.

ngolden · Answer

After using this solution for the entire day, I can say that the issue isn't gone but delayed by a lot.

Meaning that now I get disconnected and immediately connected again to the device around once 1-2 hours.

ngolden · Answer

I have done the following after talking with Dell support:

Dell Cares: Turn the U4021QW off
Disconnect every USB peripheral device from the U4021QW
Disconnect every cable (including power cable) from the U4021QW
Press and hold in the U4021QW power button for 8 seconds

Reconnect the power cable to the U4021QW
Reconnect ONLY the Thunderbolt 4/USB-C active cable to the U4021QW
Connect the other end of the Thunderbolt 4/USB-C active cable to the already turned on Laptop
Turn the U4021QW on.

I just got back from work an hour ago and haven't seen the issue so far, I'll keep reporting here, since it might be triggered from a switch or other changes to the monitor input.

Regarding the other issue with DDPM when trying one of the different layouts, I'm getting the message below:

Error with number: -10006

Write Operation Denied. The current process is not settable.

DELL-Chris M · Answer

dcbogdan,

Are you saying that you have the U3818DW and the U4021QW?

On the Windows OS side, we offered three U3818DW M3B106 firmware. All with different release dates.

Windows OS M3B106 22P8D, 8.25 MB, November 19, 2020, no longer available
Windows OS M3B106 CTF4V, 8.37 MB, November 20, 2020
Windows OS M3B106 Y3NHC, 8.37 MB, March 18, 2021

On the macOS side, we only offered one firmware update.

macOS M3B106 D7CK0, 7.43 MB, July 5, 2021

ngolden · Answer

After several weeks I can say that the TB3 connection issue with the Mac M1 Pro as been resolved completely (given the workaround I used).

The issue with the DDPM remains. In addition, I have found another issue, after a long time of use the Keyboard and Mouse which connected directly to the screen are not responding (you see they have power since the leds are on), in order to resolve this I need to connect and disconnect the TB3 cable to the Mac. If after around 1-2 hours the problem arise again I'm restarting the MacOS which give me again few days of flawless work.

Lucky we have this forum and Dell support to answer all my issues

@DELL-Cares

DELL-Chris M · Answer

* The U4021QW is passive, meaning it awaits the handshake polling from the macOS PC. It sounds like the macOS PC is stopping the handshake?

The split screen option in DDPM is working only in windows. In Mac I am getting an error about write permission.
* The team needs to know what macOS applications are use in Easy Arrange when the write operation is denied?

Monitors

U4021QW, MacBook Pro M1 Pro, connection dropping

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