Arch Linux

Cactus_Chaos

Member

Registered: 2020-09-02

Posts: 12

3 External Monitors on Intel Graphics

Hi All,

I have a thinkpad T480 (no dedicated gpu) and a thinkpad usb c gen 2 dock. I would like to connect 3 monitors to the dock (2 dp and 1 hdmi) I understand the intel display drivers can run up to 3 screens.

I can get two monitors and the laptop screen working fine, however when I plug in the third monitor it does not work. I have tried the suggestion to ignore on screen close (in /etc/systemd/logind.conf) however that does not help.

The challenge appears to be how to disable the internal monitor so that the intel graphics can output to the external monitors.

Output of:

xrandr | grep connected

Is:

eDP-1 connected (normal left inverted right x axis y axis)

DP-1 disconnected (normal left inverted right x axis y axis)

HDMI-1 disconnected (normal left inverted right x axis y axis)

DP-2 disconnected (normal left inverted right x axis y axis)

HDMI-2 disconnected (normal left inverted right x axis y axis)

DP-2-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 598mm x 336mm

DP-2-2 connected (normal left inverted right x axis y axis)

DP-2-3 connected 1920x1080+3840+0 (normal left inverted right x axis y axis) 598mm x 336mm

I have tried

xrandr --output <name of the display> --off

Any ideas on how I could make it work would be greatly appreciated!

Lone_Wolf

Forum Moderator

From: Netherlands, Europe

Registered: 2005-10-04

Posts: 11,920

Re: 3 External Monitors on Intel Graphics

Is the dock running latest firmware ?

USB C / thundetbolt docsk only support DP, if there are hdmi outputs on the dock that's because the dock has an internal DP > HDMI converter .
The quality/reliability of those converters varies ...

Do things work if you connect the HDMI screen directly to the laptop and just the 2x DP monitors through the dock ?

Welcome to archlinux forums

Last edited by Lone_Wolf (2021-07-26 11:17:07)

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Disliking systemd intensely, but not satisfied with alternatives so focusing on taming systemd.

(A works at time B)  && (time C > time B ) ≠  (A works at time C)

Cactus_Chaos

Member

Registered: 2020-09-02

Posts: 12

Re: 3 External Monitors on Intel Graphics

Hi,

Thanks for your reply. Should be as only purchased a couple of weeks ago, it is a ThinkPad USB-C Dock Gen 2.

I tried just now and only the 2 monitors connected via display port worked.

The monitor connected directly via hdmi did not even show up, wheres when connected through the dock at least all 3 monitors show up as connected displays.

Thanks in advance

Lone_Wolf

Forum Moderator

From: Netherlands, Europe

Registered: 2005-10-04

Posts: 11,920

Re: 3 External Monitors on Intel Graphics

https://support.lenovo.com/nl/en/soluti … vice-parts

It shows there are some limits to supported resolutions when using 3 monitors . could that be the issue ?

The latest firmware it links to is from 13 Apr 2021 and does include a fix for hdmi . I hope you can still use windows on this laptop ?

---

Disliking systemd intensely, but not satisfied with alternatives so focusing on taming systemd.

(A works at time B)  && (time C > time B ) ≠  (A works at time C)

Cactus_Chaos

Member

Registered: 2020-09-02

Posts: 12

Re: 3 External Monitors on Intel Graphics

Nope, only 1080p!

I will begrudgingly switch to windows and see if the firmware update helps!

Cactus_Chaos

Member

Registered: 2020-09-02

Posts: 12

Re: 3 External Monitors on Intel Graphics

Ok so using the intel graphics contoller I was able to turn off the laptop screen and get the third output....but it was limited to 50p and only output at what looked like 720p (I'd assume same resolution as the laptop screen) so no cigar. Oh well thanks for your help!