U2419H, macOS Catalina, DP 1.4 disabled

Question

Hi

I am looking far and wide to get the MST with DisplayPort to work with my two Dell U2419H monitors (very nice).

Setup: Thunderbolt 3-->1st U2419H DP1.4 --> DP1.4 to 2nd U2419H

It works with the MacBook Pro 16" seeing both monitors as one monitor, but not two monitors. But I want to have one monitor normal and the other at 90 degrees. MST is on so that is why I guess both monitors work. But when I try to enable the DP1.4 on the U2419H OSD of the first monitor the option does not change. Is this an incompatibility issue?

Also as the extended desktop it think the monitors mirror each other. So not what I have in mind.

If I use two thunderbolt 3 to dp1.4 cables from separate ports in the MacBook I get the result I want. 2 separate monitors detected. I can arrange them and rotate on, etc.

Can I not get the MST daisy chain to work? Because the 2 cable solution eats up my limited MacBook thunderbolt 3 ports

gloss · Accepted Answer

After a while on this I will like to mark this as the solution. For having 2 U2914H Dell monitors in different orientations (1 normal, 1 rotated 90 degrees):

- for Mac Catalina and MacBook Pro 16" you must have 2 thunderbolt 3 to hdmi or displayport cables from the MacBook.

- for Dell 7400 latitude windows 10 you also need two cables as well but one USB-c to HDMI/displayport and the other HDMI to HDMI as the laptop does not have 2 USB-c or 2hdmi ports.

The reason is the systems above and these monitors do not seem to be daisy chain MST compatible, even after changing resolution and cables and multiple different sequences to enable/disable settings on the laptop and the monitor.

Finally, it may work I think, but because it is giving so much trouble to setup, I suspect daisy chained MST will not be stable as I have read in other posts (not surviving reboots, system upgrades, etc.).

However the above 2 cable method seems to be stable and flawless. The only issue is you lose ports on the laptop - more so the Mac as it only has 4 thunderbolt 3 ports where 2 will be lost to the monitors and 1 for power charging, leaving only one free port. Hence a MacBook hub is needed to add more ports for such a setup.

gloss · Answer

UPDATE: these Monitors are 2 Dell U2419H and I also tested this on Windows 10 Dell Latitude  and the DP1.4 does not want tot Enable on the U2419H OSD

DELL-Chris M · Answer

Understand, DP 1.4 Enabled is the Factory default. You had to manually do the following to change it from DP 1.4 to DP 1.1a =

* Open the OSD Menu
* Under Input Source selection, press and hold DP select for 8 seconds to change the monitor setting from DP 1.4 to DP 1.1a

So repeat that and change it back to DP 1.4.

The macOS has never allowed MST daisy chain, so you will have to use the two TB3 to DP cables from separate ports in the MacBook.

gloss · Answer

Hi Chris

So I am sorry if I was not clear. I want to enable DP1.4

I did your instructions before posting and the option on the screen is "DP 1.4?" With the disabled selected and I cannot get it to change to enabled.

As I said I still have the MST daisy chain issue with my Dell latitude windows 10 machine.

So why is this the case?

DELL-Chris M · Answer

I think that is telling you that DP 1.4 is enabled. It then gives you the 'option' to disable DP 1.4. To test this, can you confirm/select the disabled selection to see what it does? Does it pop into DP 1.1a. Then it shows, disable, then confirm disable to pop back to DP 1.4.

gloss · Answer

Hi Chris

So I tried it and did not say anything about DP1.1a. This is what happened:

- I went to disable DP1.4? and I surprisingly got the option to enable DP1.4. So I did and I added MST on. With the daisy chaining the result is the same on the Mac Catalina - just one extended desktop not to additional monitors.

- Then I looked at the OSD DP1.4? setting and it was on disabled and cannot change. So I followed your instructions below and disabled it. The screen flashed but it stayed on the same result - DP1.4? Disabled, no change as from before - basically it is always saying DP1.4? with Disabled highlighted.

- I redid the steps above with my Dell Latitude 7400 Windows 10. Same results.

So I am confused as to what is the capability of these monitors as it regards to Daisy chaining; even on Dell Latitude 7400 and Windows 10?????

Any suggestions are welcomed. Otherwise I think we will have to close this thread as unanswered. Or state for this setup on a Mac and even Windows10 you need 2 separate cables to each monitor.

jphughan · Answer

@gloss  Not sure why you can't get MST enabled on your display, but as mentioned above, macOS itself does not support DisplayPort MST for daisy chaining.  A mirrored signal is what you get when you connect a daisy chain setup to a system that doesn't support daisy chaining, since the system isn't able to treat the daisy chained displays independently.  Ironically if you were to install Boot Camp on your Mac so that it ran Windows, then while running Windows you WOULD be able to use a daisy chain -- so the hardware support it, but Apple has chosen not to add support for it to macOS itself.  There have been complaints about this for years here, on Apple's forums, on Reddit, and elsewhere.

gloss · Answer

@jphughan as I noted, I am having the same results with a Dell latitude 7400 with windows 10. I can get it as a single extended display, but not as separate monitors.  Very strange I think.

jphughan · Answer

@gloss  Try disconnecting the cable connected to the MST output of the first display, then resetting it to factory defaults, then see if you can enable MST before connecting the cable to the MST output again.

gloss · Answer

@jphughan MST is not the issue it is the DP1.4? Option is the issue.  I tried the cable disconnect as well.

ittakes2bananas · Answer

Hey Chris, I found this while troubleshooting my dell u4021qw. I am attempting to connect my Mac Mini 2018 to the display via a Thunderbolt USBC to DisplayPort cable. One of the tips I saw was to try changing the DP setting from 1.4 to 1.2. I can do this with the Thunderbolt input via the OSD menu.

However, I can't change the DisplayPort setting via OSD. As soon as I press and hold on the DP input option via OSD, it switches to the input and the OSD menu disappears. At this point, it says "no input detected" for the DP input and the OSD menu gets wonky — I can no longer get into the input settings properly.

Any idea what might be going on?

Monitors

U2419H, macOS Catalina, DP 1.4 disabled

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