U2414H DisplayPort Daisy Chain / MST Resolution: How I fxed it (workaround)!

Dear topic readers, Hi folks,

Last days I've spent some time setting up my 3 Dell U2414H's in Daisy Chain / MST mode.

I've had the same issues as people in this topic: U2414H DisplayPort Daisy Chain/MST Resolution Issue.

For me it turns out the monitors weren't detected correctly, so Windows uses a "Default Monitor", however, for some reason, this monitor will be set to a resolution of 1600x1200, this causes the U2414H to turn into "power saving" mode because it can't handle the -too- high resolution.

Ive managed to fix this problem by changing the resolution of the "Default Monitor" from 1600x1200 to 1920x1080.

Below the workaround that I've used to get my configuration working.

Sorry for my lack of English, my native language is Dutch.

IMPORTANT NOTE: The workaround below contains Windows Registry mods and can serious damage your PC!
Only apply this workaround when you really know what you're doing!
Neither Dell, nor I are responsible if you're messing up your PC!

First of all, we need to make some system changes to Windows, so we must run every program we need in Administrator mode.

1)     Click the Windows orb (a.k.a. Start Button) and type cmd, then Right click the cmd.exe result and select [Run as Administrator]

Now we're gonna use some "Easter Eggs" in Windows.

Lets's tell Windows to show it's "disconnected" Devices.

2)     Enter the following commands and press [Enter] after every command

> set devmgr_show_nonpresent_devices=1
> devmgmt.msc

Don't close this window.

Windows device manager will be started but the "disconnected" devices are not visible yet, to fix this, take the following steps:

3)     Click [View] followed by [Show hidden devices], so this item will show a checkmark.

4)     Open the [Monitors] section, this is possibly a mess, like this

As you can see, there are (possibly) a lot of hidden [Generic Non-PnP Monitor] entries.

IMPORTANT NOTE: Other guides on the internet describe to remove ALL hidden entries, here's my advise:
DON'T! Please read on to see why.

Now we have confirmed that Windows was not able to setup (every) screen correctly, we're gonna tell Windows to apply the right settings, next time it doesn't recognize the monitor(s).

5)     Switch back to the elevated command window and enter the following command:

> regedit

6)     The Windows registery editor will be started, find the following key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\DISPLAY\Default_Monitor

This entry contains one or more sub entries with a long number as name:

Keep the regedit window open and switch back to the device manager window, position the windows aside to see wat happens.

Start removing the hidden [Generic Non-PnP Monitor] entries in device manager one-by-one, you'll see that the child entries from [Default_Monitor] in regedit are also disappearing (Maybe you have to focus the regedit window and press F5 to refresh the entries manually).
Repeat this step until you have only one entry remaining, if available the only connected and visible [Generic Non-PnP Monitor].

It's important to keep at least one [Generic non-PnP Monitor] to make sure Windows will communicate to the monitor(s) at the right resolution to prevent the monitor to go into "power saving" mode.

7)     Switch to the regedit window and open the [DeviceParameters] entry of the (first and only) [Default_Monitor] child entry

As you can see, there is a key named BAD_EDID, so, if Windows is not able to get the monitor's EDID, it will fall back to this entry.

Now, take a look at the [Device Parameters] key. There can be two situations (8A or 8B)

8A)     The (grand)child entry is named the wrong resolution, e.g. 1600,1200, we have to rename it.

Right click the entry with the wrong resolution, e.g. 1600,1200 and click [Rename].
Now change the name to 1920,1080

8B)     There is no child entry, so we have to create it

Right click the [Device Parameters] entry, click [New] followed by [Key].
Now enter the name MODES.

Richt click the created [Modes] entry, click [New] followed by [Key] and enter the name 1920,1080.

If you have alreay some DELAXXX entries, make sure that every entry with the wrong resolution is changed to the right one: 1920,1080

OK, That's it.

Let's see if it worked

Now try to turn your displays on and off (in different order) and try to restart your PC (multiple times).

In my case, with 3 U2414H's in Daisy Chain mode my results are:

09)     Device manager:

10)     Windows display setup:

11)     Intel DisplayPort topology (sorry it's in Dutch)

12)     Regedit

Good to know:

Make sure the last monitor in the Daisy Chain is set to DisplayPort 1.2: OFF!

Also good to know:

There is a possibility that you will see more entries aside of [Default_Monitor] and [DELA0A3].

According to the Dell display driver, this are the enumerations used by Dell:

HDMI1 - DELA0A4
HDMI2 - DELA0B2
DisplayPort - DELA0A2
miniDisplayPort - DELA0A3

So if you have connected your monitor another way, you will see entries of this connection as well.

When using another input port on your monitor to configure your DisplayPort (DaisyChain, MST) setup, make sure to unplug this port before entering DisplayPort mode. It look likes the monitor is reporting the same ID on all ports, so Windows can be confused when it detects the same ID on both DP as e.g. HDMI.

Conclusion

This is what worked for me. I hope to help you people by sharing this experience and maybe some Dell technicians can use this information to reproduce the problem and fix it permanently..

 

Regards,

Matthijs de Ridder, Netherlands
a.k.a. mastermattie