Ubuntu desktop screen flashing after upgrade, X server won't start, low graphics mode etc. 

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04/07/2009
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September 23, 2014 22:33:08    Last update: September 23, 2014 22:36:21
I upgraded Ubuntu to 14.04 (accepted all defaults when prompted), but then the desktop just refused to start. It's flashing black screen and some desktop image. It won't even boot in recovery mode! I booted in command line to troubleshoot. After a day or two playing with it, I decided that might be caused by an incompatible video driver.

Some good information is available here: https://wiki.ubuntu.com/X/Troubleshooting/VideoDriverDetection.

I copied some text here for reference cause I can't say it better.

  1. Determine the PCI ID of the chip:

    $ lspci -nn | grep VGA
    01:00.0 VGA compatible controller [0300]: ATI Technologies Inc RV535 [Radeon X1650 Series] [1002:71c7] (rev 9e)
    


    Here, the PCI ID is 1002:71c7.

  2. Now look in the PCI ID registry to see which driver is used. (Drop the colon ':' when doing this.)

    $ grep -i 100271c7 /usr/share/xserver-xorg/pci/*.ids
    
    /usr/share/xserver-xorg/pci/radeon.ids:100271C7
    


    This indicates that X would pick the -radeon driver for me. If you did not get output, then your chip is not currently supported by any driver.
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