Additional options for the radeon driver

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

External Monitors

You can use MergedFB to provide dualhead Xinerama-like setups. MergedFB's pseudo-Xinerama is not Xorg server's Xinerama. You don't have to enable Xorg server's Xinerama to use MergedFB's pseudo-Xinerama. However, applications compiled with Xinerama support (Gentoo users USE="xinerama") can interpret pseudo-Xinerama hints, for example, to maximize to a single monitor instead of spanning two monitors.

The following (partial) Xorg config will make the Radeon card use 1024x768 on the internal lcd display and 1280x1024 on the external (Note: only one screen/monitor section is needed (it controls the setup of the internal monitor) even though we have two displays): N.B.: Modes used in the MetaModes also have to be present in the screen modes section.

Section "Device"
        Identifier      "ATI"
        Driver          "radeon"
        # accelration
        Option          "AGPMode" "4"
        Option          "EnablePageFlip" "on"
        Option          "RenderAccel" "on"
        # enable (partial) PowerPlay features
        Option          "DynamicClocks" "on"
        # use bios hot keys on thinkpad (aka fn+f7)
        Option          "BIOSHotkeys" "on"
        # enable radeon specific xinerama
        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 "InternalLCD"
        Option "DPMS"
EndSection
Section "Screen"
        Identifier "Default Screen"
        Device "ATI"
        Monitor "InternalLCD"
        DefaultDepth 24
        SubSection "Display"
                Depth 24
                Modes "1024x768"
        EndSubSection
EndSection

Note: 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.

External Monitors and Docking Stations/Port Replicators

I seems that Xorg incorectly discovers the external displays when connected to a docking station/port replicator - the only solution to this problem (at least that I know of) is to start the laptop (and boot all the way into X) prior to inserting it in the dock.

It also happens that if you are attempting to use the mergedFB trick to do dual head with out a docking station, you have to start X on the laptop LCD first, then plug a monitor into the VGA port. If the external monitor is already plugged in, the internal LCD will be blank.

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)
• Xorg bug DynamicClocks may hang your machine

Color Tiling

ColorTiling is supposed to be enabled by default. But, it looks like setting it explicitely to "on" increases the FPS in glxgears.

        Option          "ColorTiling"   "on"

Acceleration Architecture

By default, the XAA architecture is used. EXA is newer and supposed to have better performance. It looks like it reduces the FPS in glxgears (maybe because it disables Page Flip) but makes the Composite extension be fast.

       Option          "AccelMethod"   "EXA"

Page Flip

Page Flip increases performance but is not always supported. It will be disabled if the EXA architecture is used.

        Option          "EnablePageFlip"        "on"

Related Links

• xorg 6.8.2 Radeon manual page