configure unknown/unrecognised external monitor

How to configure settings for unknown monitor?
When I have unknown monitor connected, how can I increase resolution to match device connected?

When monitor correctly communicates with the graphics card and system the modes supported will correctly appear and monitor will correctly be configured. In current linux distros hardware settings for x-server are by default done without use of configuration file. After attaching a new monitor we can configure it automatically just by switching to terminal and back to graphics terminal to softly restart the xserver e.g. (Ctrl-Alt-F1), (Ctrl-Alt-F8). A better way it probably to use the monitor preferences command in the start menu (Found in gnome start menu under System>Preferences>Monitors). However if supported modes are not found then there is a useful command line tool we can use to add the supported mode to xserver.

In my case after attaching “gateway” monitor to my lenovo t410 laptop by VGA shaped port only the following resolutions were available. If software configuration is not possible then a hardware solution is to select 1:1 video scaling in menu of the monitor to prevent smearing of pixels.

Available resolutions for unknown monitor:

I found following example::

$ xrandr
Screen 0: minimum 320 x 200, current 1368 x 768, maximum 8192 x 8192
VGA1 connected 1368×768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
1368x768_60.00 59.9*+
1024×768 60.0
1024x768_60.00 59.9
800×600 60.3 56.2
848×480 60.0
640×480 59.9
1280x800_60.00 59.8

$ cvt 1440 900
$ xrandr –newmode “1440x900_60.00” 106.50 1440 1528 1672 1904 900 903 909 934 -hsync +vsync
$ xrandr –addmode VGA1 1440x900_60.00

I issued following commands to add support of my monitor::

We want to add a mode to support the resolution of external monitor which in this case is 1680×1050. If we issue “cvt” command we will be informed of the correct “modeline” options we need to issue with “xrandr”.

>cvt 1680 1050

# 1680×1050 59.95 Hz (CVT 1.76MA) hsync: 65.29 kHz; pclk: 146.25 MHz
Modeline “1680x1050_60.00” 146.25 1680 1784 1960 2240 1050 1053 1059 1089 -hsync +vsync
xrandr –newmode “1680x1050_60.00” 146.25 1680 1784 1960 2240 1050 1053 1059 1089 -hsync +vsync
xrandr –addmode VGA-1 1680x1050_60.00

After issuing the final command we can select the mode of the monitor (and select relative position etc, etc) using the “monitor preferences” tool. Found in gnome start menu under System>Preferences>Monitors. This tool can be added to the start panel if desired.

Monitor preferences tool, gnome menu

Position of gnome monitor preferences tool, gnome menu, gnome desktop.

Monitor preferences tool

Monitor preferences tool

Monitor icon/applet

Monitor icon/applet

alternative tools exist, e.g. grandr is another graphical tool to see monitor settings.




5 Responses

  1. Reblogged this on anthonyvenable110.

  2. Nice and informative post. I am using laptops at home for almost 15 years now, and since I switched to smaller (13 inch) models I hook them up on an external monitor at home. On my last laptop I was running debian and had some issues with hooking it up. Now I switched to a MacBook and found out that the procedure is a little bit easier (I wrote an article on that if you are interested: However, I will safe your post in my archive, just in case my next laptop will be a “Linux” machine again 😉

  3. Thanks bluewoodtree, I thought it would be harder to set up for external monitor because when I tried before xorg.conf had to be edited to do it. Now on linux everything should be detected when xorg starts so it seems to work better without any configuration file.

    One you know that this tool exists it is really easy to have multiple configurations.

    There is generally no need to issue commands on the command line, instructions above are to deal with my cheaper monitor which isn’t automatically recognised.

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