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I have a Dell XPS 9550. It has a 4K screen, which works great on Ubuntu. However, when I plug in an external 4K monitor (specifically, a Kogan 28" 4K LED Monitor), the highest resolution available is only 1920x1200. :(

Some info:

  • Running Ubuntu 17.10 with kernel 4.10.0-26-generic
  • Using HDMI cable that came with monitor
  • Using nvidia-375.66 drivers

I tried the steps outlined in this answer:

$ cvt 3840 2160
# 3840x2160 59.98 Hz (CVT 8.29M9) hsync: 134.18 kHz; pclk: 712.75 MHz
Modeline "3840x2160_60.00"  712.75  3840 4160 4576 5312  2160 2163 2168 2237 -hsync +vsync
$ xrandr --newmode "3840x2160_60.00"  712.75  3840 4160 4576 5312  2160 2163 2168 2237 -hsync +vsync
$ xrandr --addmode HDMI-1-1 3840x2160_60.00

However when I try to select 3840x2160, my laptop screen becomes very stretched, and both the external & laptop screen start turning on/off repeatedly.

setting 3850x2160 resolution

Stretched laptop screen

Any idea how I can fix this? Let me know if you need any more information.

Thanks! :)

Ben B
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1 Answers1

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The issue seems to be with the laptop's HDMI port, which does not support 4K@60Hz.

However, you can get 4K@60Hz over the USB Type-C port if you use an adapter, such as the official Dell one.

I'm not too sure if these work with Linux, however.

Here's some threads online where people discuss the issue:

Ben B
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