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akita16384 Registered User


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HOWTO: Ubuntu / Linux users using netbooks with external monitors akita16384 Oct 5th, 09, 06:44 PM #1

Hi folks,

Thought I would share a tip for setting up netbooks with external monitors.
This is a HOWTO guide for those with difficulty. If it already works for you, move along.

Summary
To add an external monitor and have a supported resolution made available, you need to:
  1. Install xrandr and cvt
  2. Determine the modeline using cvt
  3. Add the new modeline using xrandr
  4. Add the new modeline to the output that the monitor is attached to
  5. Test out the output
  6. Save the settings to persist over reboots

Apps needed:
1. Xrandr
2. cvt

Install both apps using apt-get if you do not have them already:

Code:
$ sudo apt-get install xrandr cvt
Setup a *supported* mode for use by Xrandr

Use cvt to determine the modeline info:

Syntax: cvt xres yres refreshrate
eg,
Code:
$ cvt 1920 1200 60
# 1920x1200 59.88 Hz (CVT 2.30MA) hsync: 74.56 kHz; pclk: 193.25 MHz
Modeline "1920x1200_60.00"  193.25  1920 2056 2256 2592  1200 1203 1209 1245 -hsync +vsync
Copy the text "1920x1200_60.00" 193.25 1920 2056 2256 2592 1200 1203 1209 1245 -hsync +vsync with the quotes

Add the newmode to xrandr

Add this new mode into xrandr at the terminal. In the example below, I modified the label/name, removing the "_60.00". You can call it whatever you want.

Code:
$ xrandr --newmode "1920x1200"  193.25  1920 2056 2256 2592  1200 1203 1209 1245 -hsync +vsync
Add this newmode to the monitor resolution list

For this new resolution to be selectable by the monitor, you need to add it to the output that the monitor is attached to. The following example has the monitor attached to output VGA-0. Yours may be VGA, DMI or something else. (Note to self: update this with link to show how to determine the right label).

Code:
$ xrandr --addmode VGA-0 "1920x1200"
Test out the new resolution

We are ready to test out the new resolution. But before we test it out, you need to know how to restore it to a working resolution first.

Code:
$ xrandr --output VGA-0 --mode 1024x768
The above would restore your output to 1024x768, assuming that your monitor was able to display at this resolution.

Now, let us test out the SUPER HIGH resolution. Now, you would want to use only settings that your monitor support. If you set it wrongly, don't come blaming me for any problem. :p

Code:
$ xrandr --output VGA-0 --mode 1920x1200
If it is a supported mode for both your graphics chipset and monitor, your external monitor should display nicely. If it is an analog VGA connection, you may need to sync the display. If it is DMI, then you do not need to do so.

If this failed, you will get a blank screen with "unsupported" or something and Ubuntu will restore your settings after timing out. If it is not even supported by your GPU, then Ubuntu will possibly *hang* ... in which case, do a hard reset and everything is back to normal.

Everything worked and I want this setting to persist reboots

I currently save my settings in ~/.xprofile

Code:
xrandr --newmode "1920x1200"  193.25  1920 2056 2256 2592  1200 1203 1209 1245 -hsync +vsync
xrandr --addmode VGA-0 "1920x1200"
xrandr --output VGA-0 --mode 1920x1200

xrandr --newmode "1680x1050"  146.25  1680 1784 1960 2240  1050 1053 1059 1089 -hsync +vsync
#xrandr --newmode "1680x1050"  160.00  1680 1792 1968 2256  1050 1053 1059 1093 -hsync +vsync
xrandr --addmode VGA-0 "1680x1050"
#xrandr --output VGA-0 --mode 1680x1050
You can store many supported modes inside this file, but you should set the output *ONCE*. You can see from my .xprofile file above the various configurations I have and an output setting disabled as a comment.

You can also store the settings in kdm/gdm startup scripts or xorg.conf files. Refer to the reference link below for more info.

Summary
To add an external monitor and have a supported resolution made available, you need to:
  1. Install xrandr and cvt
  2. Determine the modeline using cvt
  3. Add the new modeline using xrandr
  4. Add the new modeline to the output that the monitor is attached to
  5. Test out the output
  6. Save the settings to persist over reboots

Reference:
https://wiki.ubuntu.com/X/Config/Resolution
WSXGA Wide XGA+ - Wikipedia, the free encyclopedia


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Last edited by akita16384; Oct 5th, 09 at 07:08 PM..
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