Pour les cartes inférieurs à ATI 9200se c'est AIGLX avec le driver Radeon qu'il faut utiliser à la place de XGL (c'est la même chose mais optimisé pour le driver libre).
L'avantage, outre le fait de rester dans le libre, c'est que l'on garde la possibilité de faire tourner des soft utilisant l'open GL (économiseurs d'écrans, jeux, softs pro). Si on veut désactiver compiz une petite icone dans la barre de notification fait ça instantanemment.
Le liens vers AIGLX:
http://doc.ubuntu-fr.org/applications/aiglx
Et à titre d'exemple mon Xorg.conf (je tourne sur un protable avec un écran 1400x1050 alors attention au copier/coller. En plus ce Xorg permet de detecter lorsqu'on branche un écran externe et de descendre la résolution automatiquement à 1280x1024):
# /etc/X11/xorg.conf (xorg X Window System server configuration file)
#
# This file was generated by dexconf, the Debian X Configuration tool, using
# values from the debconf database.
#
# Edit this file with caution, and see the /etc/X11/xorg.conf manual page.
# (Type "man /etc/X11/xorg.conf" at the shell prompt.)
#
# This file is automatically updated on xserver-xorg package upgrades *only*
# if it has not been modified since the last upgrade of the xserver-xorg
# package.
#
# If you have edited this file but would like it to be automatically updated
# again, run the following command:
# sudo dpkg-reconfigure -phigh xserver-xorg
Section "Files"
FontPath "/usr/share/X11/fonts/misc"
FontPath "/usr/share/X11/fonts/cyrillic"
FontPath "/usr/share/X11/fonts/100dpi/:unscaled"
FontPath "/usr/share/X11/fonts/75dpi/:unscaled"
FontPath "/usr/share/X11/fonts/Type1"
FontPath "/usr/share/X11/fonts/100dpi"
FontPath "/usr/share/X11/fonts/75dpi"
# path to defoma fonts
FontPath "/var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType"
EndSection
Section "Module"
Load "i2c"
Load "bitmap"
Load "ddc"
Load "dri"
Load "extmod"
Load "freetype"
Load "glx"
Load "int10"
Load "type1"
Load "vbe"
Load "dbe"
EndSection
Section "Extensions"
# Option "RENDER" "Enable"
Option "Composite" "Enable"
EndSection
Section "InputDevice"
Identifier "Generic Keyboard"
Driver "kbd"
Option "CoreKeyboard"
Option "XkbRules" "xorg"
Option "XkbModel" "pc105"
Option "XkbLayout" "fr"
Option "XkbVariant" "latin9"
EndSection
Section "InputDevice"
Identifier "Configured Mouse"
Driver "mouse"
Option "CorePointer"
Option "Device" "/dev/input/mice"
Option "Protocol" "ExplorerPS/2"
Option "ZAxisMapping" "4 5"
Option "Emulate3Buttons" "true"
EndSection
Section "InputDevice"
Identifier "Synaptics Touchpad"
Driver "synaptics"
Option "SendCoreEvents" "true"
Option "Device" "/dev/psaux"
Option "Protocol" "auto-dev"
Option "HorizScrollDelta" "0"
EndSection
Section "InputDevice"
Driver "wacom"
Identifier "stylus"
Option "Device" "/dev/wacom" # Change to
# /dev/input/event
# for USB
Option "Type" "stylus"
Option "ForceDevice" "ISDV4" # Tablet PC ONLY
EndSection
Section "InputDevice"
Driver "wacom"
Identifier "eraser"
Option "Device" "/dev/wacom" # Change to
# /dev/input/event
# for USB
Option "Type" "eraser"
Option "ForceDevice" "ISDV4" # Tablet PC ONLY
EndSection
Section "InputDevice"
Driver "wacom"
Identifier "cursor"
Option "Device" "/dev/wacom" # Change to
# /dev/input/event
# for USB
Option "Type" "cursor"
Option "ForceDevice" "ISDV4" # Tablet PC ONLY
EndSection
Section "Device"
Identifier "ATI Technologies, Inc. Radeon R250 Lf [Radeon Mobility 9000 M9]"
Driver "radeon"
BusID "PCI:1:0:0"
Option "XAANoOffscreenPixmaps"
Option "AGPMode" "4"
Option "AGPSize" "64"
Option "RingSize" "8"
Option "BufferSize" "2"
Option "DynamicClocks" "True"
Option "MergedFB" "true"
Option "MetaModes" "1280x1024"
Option "DesktopSetup" "Horizontal"
Option "CRT2Position" "Clone"
Option "NoTV" "yes"
Option "MonitorLayout" "LVDS, CRT"
EndSection
Section "Device"
Identifier "ATI R250 2nd"
Driver "radeon"
BusID "PCI:1:0:0"
Screen 1
EndSection
Section "Monitor"
Identifier "Generic Monitor"
Option "DPMS"
EndSection
Section "Monitor"
Identifier "External Monitor"
Option "DPMS"
HorizSync 31.5-80.5
VertRefresh 20-60
EndSection
Section "Screen"
Identifier "Default Screen"
Device "ATI Technologies, Inc. Radeon R250 Lf [Radeon Mobility 9000 M9]"
Monitor "Generic Monitor"
DefaultDepth 16
SubSection "Display"
Depth 1
Modes "1400x1050"
EndSubSection
SubSection "Display"
Depth 4
Modes "1400x1050"
EndSubSection
SubSection "Display"
Depth 8
Modes "1400x1050"
EndSubSection
SubSection "Display"
Depth 15
Modes "1400x1050"
EndSubSection
SubSection "Display"
Depth 16
Modes "1400x1050"
EndSubSection
SubSection "Display"
Depth 24
Modes "1400x1050"
EndSubSection
EndSection
Section "Screen"
Identifier "External Screen"
Device "ATI R250 2nd"
Monitor "External Monitor"
DefaultDepth 24
SubSection "Display"
Modes "1280x1024" "1024x768" "800x600" "640x480"
EndSubSection
EndSection
Section "ServerLayout"
Identifier "Default Layout"
Screen "Default Screen"
InputDevice "Generic Keyboard"
InputDevice "Configured Mouse"
InputDevice "stylus" "SendCoreEvents"
InputDevice "cursor" "SendCoreEvents"
InputDevice "eraser" "SendCoreEvents"
InputDevice "Synaptics Touchpad"
Option "AIGLX" "true"
EndSection
Section "ServerLayout"
Identifier "External Layout"
Screen "External Screen"
Screen "Default Screen"
InputDevice "Generic Keyboard"
InputDevice "Configured Mouse"
InputDevice "stylus" "SendCoreEvents"
InputDevice "cursor" "SendCoreEvents"
InputDevice "eraser" "SendCoreEvents"
InputDevice "Synaptics Touchpad"
Option "AIGLX" "true"
EndSection
Section "ServerLayout"
Identifier "Dual Layout"
Screen "Default Screen"
InputDevice "Generic Keyboard"
InputDevice "Configured Mouse"
InputDevice "stylus" "SendCoreEvents"
InputDevice "cursor" "SendCoreEvents"
InputDevice "eraser" "SendCoreEvents"
InputDevice "Synaptics Touchpad"
Option "AIGLX" "true"
option "MergedFB" "true"
EndSection
Section "DRI"
Mode 0666
EndSection
O-p