Thunderbolt 3 dual hdmi adapter on Fedora 25


#1

I recently bought the thunderbolt 3 to dual hdmi adapter. Although it stated that only windows is supported, I got triggered by some Amazon review, stated he got it working on Ubuntu.
My configuration

  • Dell Precision 5510 laptop with HDMI and thunderbolt output
  • Running fedora 25 - fully updated
  • Updated the bios to the latest version
  • Using the default nouveau drivers.

Result:

  • When only using the plugable adapter, I get output on my 2 external monitors + laptop screen. Great!
  • When using the plugable adapter and the additional hdmi laptop output, I only get output on 2 monitors + laptop screen. When unplugging the hdmi laptop output, it switches back to the plugable adapter.

Question:
Is there a way to use 3 external monitors + laptop screen?


#2

Hi Joris,

Thanks for posting! I am glad the adapter is working properly with your system, and appreciate the great detail you provided about your setup.

While we don’t have your system in house to test with, the short answer is most likely no, you will not be able to use three external monitors in the setup you describe. The reason for the behavior you are seeing is most likely a hardware limitation of your Dell system, in that when devices are directly connected to the internal GPU (via the Thunderbolt 3 port or the built-in HDMI port) the system design is limited to three total displays, the internal and the two external.

A way to test this theory would be if you start the process with the internal display active, connect a single display to the HDMI output, and then connect the Thunderbolt adapter (only one of the two outputs will work).

Please let me know if that information helps!

Bob


#3

Hi Bob,

Thank you for the quick reply. Correct. When first connecting the hdmi output, I get 1 external monitor working. When connecting the plugable adapter after that, it shows only 1 additional monitor.
Even more, when you turn around the usb-c connector, the monitor that works with the plugable adapter switches.

Regards,
Joris


#4

Hi Joris,

Thanks for getting back with the confirmation, appreciate you taking the time to test as you have and share the results.

Please let us know if you need any help in the future!

Bob


#5

I’ve contacted Dell also to figure out why the HDMI port becomes unavailable. I hope it becomes a software issue that maybe can be fixed through an update.


#6

Hi Joris,

Thanks for getting back. While I can’t speak specifically to Dell’s design of your system, I would presume that my initial assumption is correct and it is a hardware limitation that only allows for three active displays. It may be difficult to get this level of information from Dell technical support, and the fact that you are running Fedora Linux (they only support Ubuntu on certain systems) may also prove to be a stumbling block in your communication.

Bob


#7

Thanks. Let’s hope I can get some more information on the Dell forum on what is possible.


#8

In the meantime have you tried to using xrandr (or arandr) to set output sources and such?

xrandr examples in the two links below. I believe you can disregard the DisplayLink specific information:

https://wiki.archlinux.org/index.php/…
https://wiki.archlinux.org/index.php/…


#9

I checked indeed xrandr. What is strange is that the HDMI-1 clones DP-1

HDMI-1 disconnected (normal left inverted right x axis y axis)   
Identifier: 0x74   
Timestamp: 68989114   
Subpixel: unknown   
Clones: DP-1   
CRTCs: 1 2 0   
Transform: 1.000000 0.000000 0.000000   
0.000000 1.000000 0.000000   
0.000000 0.000000 1.000000   
filter:  
aspect ratio: Automatic  
supported: Automatic, 4:3, 16:9   
Broadcast RGB: Automatic  
supported: Automatic, Full, Limited 16:235   
audio: auto  
supported: force-dvi, off, auto, on   

Currently I’m running with the nouveau and i915 drivers. So one of my next steps might be to check the proprietary nvidia drivers.


#10

Oh. does you machine have optimus?

https://wiki.archlinux.org/index.php/…

Sorry for the Arch Linux specific info. It’s just a great Linux wiki.


#11