Additional options for the radeon driver

Options for the radeon driver are documented on the radeon(4x) man page.

Dualhead capabilities

You can use MergedFB to provide dualhead xinerama like displays, the folowing (partial) config will make the readeon card use 1024x768 on the internal lcd display and 1280x1024 on the external (note only one screen/monitor section is needed even though we have two displays):

Section "Device"
        Identifier      "ATI"
        Driver          "radeon"
        Option          "MergedFB" "true"
        Option          "CRT2Position" "RightOf"
        Option          "CRT2Hsync" "50-75"
        Option          "CRT2VRefresh" "30-82"
        Option          "MetaModes" "1024x768-1280x1024"
        Option          "MergedNonRectangular" "true"
        BusID           "PCI:1:0:0"
EndSection
Section "Monitor"
        Identifier "Standardbildschirm"
        Option "DPMS"
EndSection
Section "Screen"
        Identifier "Default Screen"
        Device "ATI"
        Monitor "Standardbildschirm"
        DefaultDepth 24
        SubSection "Display"
                Depth 24
                Modes "1024x768"
        EndSubSection
EndSection

The CRT2 directives always applies for the external monitore regardless of type (LCD, CRT...). The option MergedNonRectangular is needed to force the screens into two different sizes.

AGP speed

By default, the open source radeon driver forces 1x AGP speed. Quote from the developers:

tuning to the highest speed possible has caused hangs on some boxes, with no
discernable pattern, so we default to 'slow but safe' whilst giving the option
to go fast if the user wants to try it.

Higher speeds can be enabled by adding Option "AGPMode" "X" (where X is a number) in the Device section in /etc/X11/xorg.conf.

Section "Device"
       Identifier  "Videocard0"
       Driver      "radeon"
       VendorName  "IBM Thinkpad"
       BoardName   "ATIdd Mobility FireGL 7800"
       Option      "AGPMode" "4"
EndSection

With this option enabled (set to 4x speed), the X11 server should print (/var/log/Xorg.0.log):

(**) RADEON(0): Option "AGPMode" "4"
(**) RADEON(0): Using AGP 4x mode

AGP Fast Writes

By default, the open source radeon driver disables AGP Fast Writes. Fast Writes can be enabled by adding Option "AGPFastWrite" "yes" in the Device section in /etc/X11/xorg.conf.

Section "Device"
       Identifier  "Videocard0"
       Driver      "radeon"
       VendorName  "IBM Thinkpad"
       BoardName   "ATI Mobility FireGL 7800"
       Option      "AGPFastWrite" "yes"
EndSection

Dynamic Clock scaling

Please see:

• How to make use of Graphics Chips Power Management features (save even more battery power)