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Thread: ATI fglrx driver and large displays

  1. #1
    Join Date
    Jun 2008
    Location
    Florida, USA
    Posts
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    Default ATI fglrx driver and large displays

    I have seen several posts about unreadable desktops when ATI fglrx drivers connect to large screen displays, such as HDTVs.
    I have found that the following solution works for me; it may not be the "best" way, please comment if you have a better work around.

    When the fglrx driver is installed and an initial configuration established with
    Code:
    aticonfig --initial
    several entries are made in /etc/X11/xorg.conf, including this:
    Code:
    Section "Monitor"
            Identifier   "aticonfig-Monitor[0]-0"
    
            Option      "VendorName" "ATI Proprietary Driver"
            Option      "ModelName" "Generic Autodetecting Monitor"
            Option      "DPMS" "true"
    EndSection
    It seems by default that the connected monitor characteristics are re-read each time X starts up and a configuration is dynamically set up. With very large displays (e.g. my 1600 mm x 900mm DLP), this yields a calculated DPI around 20,20 or so and the fonts are unreadible on the display. When running cloned mode with a "normal" monitor, this usually affects both displays; it becomes impossible to read anything that is font based.

    My solution is to modify xorg.conf to read
    Code:
    Section "Monitor"
            Identifier   "aticonfig-Monitor[0]-0"
    #added to force reasonable sized fonts 
            DisplaySize  400        225
    #
            Option      "VendorName" "ATI Proprietary Driver"
            Option      "ModelName" "Generic Autodetecting Monitor"
            Option      "DPMS" "true"
    EndSection
    This overrides what EDID reports to X on startup.
    You can see the result in /var/log/Xorg.0.log
    Code:
    .....
    ......
    (WW) fglrx(0): Probed monitor is 1600x900 mm, using Displaysize 400x225 mm
    (**) fglrx(0): DPI set to (121, 121)
    (--) fglrx(0): Virtual size is 1920x1080 (pitch 1920)
    .....
    .....
    There may be unexpected side effects, but I have not hit them as yet.

    If the is a more correct way to do this, please comment.

  2. #2
    Join Date
    Jun 2008
    Location
    Auckland, NZ
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    Default Re: ATI fglrx driver and large displays

    Thats a reasonable (and common) technique. If the monitor comes with a setup CD, this can be used to adjust the monitor configuration via the sax2 utility.

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