Aug 31, 2014

[Solved] External monitor unknown after updating to Ubuntu 14.04

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Finally I decide to switch to the new Ubuntu LTS 14.04 code named 'Trusty Tahr'. As usual, the switch is seamless. I just pushed the 'update distribution' button, and ubuntu takes cares of the rest. It took about an hour to download all the required files necessary to complete the installation and perform the installation scripts. And just like that it was done and ready for use again.

But wait! What happened to my external monitor? I use a Samsung, 23" external display with my old Dell Laptop. And after the reboot, the resolution on my external monitor looks horrid. I checked from the Preference -> Monitor Settings(I use LXDE as my desktop manager, if you don't you should. It's crazy fast) and it seems ubuntu is having issues identifying the monitor and it's native resolutions. Under monitor settings, the maximum resolution that was listed was 1024x768 where as the monitor can support full 1080p (1920x1080). I used xrandr and the result is the same wrong resolutions. The reason is probably a driver issue. My old laptop uses the The Mobile Intel® GM45 Express Chipset, featuring the Mobile Intel® Graphics Media Accelerator (GMA) 4500MHD. I went to intel website, to download their latest drivers, but it didn't help to solve the problem.

I thought I would force the 1920x1080 resolution on the external monitor 

So I thought I would force the 1920x1080 resolution on the external monitor and see whether it can handle that. I searched for documentation in the ubuntu wiki, and found some nifty commands to add different resolutions using xrandr. So I issued the following commands (Line that begins with ### is my comment, not a command) -


cvt 1920 1080 60
###to create a new resolution to add using xrandr.
The output of that follows -

# 1920x1080 59.96 Hz (CVT 2.07M9) hsync: 67.16 kHz; pclk: 173.00 MHz
Modeline "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync

###Copy everything from Modeline and paste it with xrandr --newmode command.

xrandr --newmode 1920x1080_60.00  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync

###Finally use addmode option to add the resolution in your xrandr list.
xrandr --addmode VGA1 "1920x1080_60.00"
###Here VGA1 is the name of the external monitor, find it by running xrandr

ubuntu for human logo Now you are done. You should be able to see this new resolution if you open 'Monitor Settings' again. Select and Apply and you can happily use the 1080p resolution once again. Remember, this is not a persistent setting. So every time, you restart you'll lose the resolution. So to avoid doing all of these over again, I saved the instructions in a bash file in my home directory and that in my .bash_profile. So it is automatically executed everytime I restart(which I don't do often).  I hope this helps and eagerly hoping that Ubuntu fixes this problem in their upcoming update.

2 comments :

  1. Had the same problem. Thanks for the post

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  2. Thanks. Got it working. Can you elaborate on how you did this : " I saved the instructions in a bash file in my home directory and that in my .bash_profile"

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