修改/etc/X11/xorg.conf：
Section "Device"
Identifier "Configured Video Device"
Driver "fglrx"
EndSection
# added
Section "Device"
Identifier "Card1"
Driver "fglrx"
EndSection
Section "Monitor"
Identifier "Configured Monitor"
EndSection
# added
Section "Monitor"
Identifier "ExtMonitor"
EndSection
Section "Screen"
Identifier "Default Screen"
Monitor "Configured Monitor"
Device "Configured Video Device"
Defaultdepth 24
EndSection
# added
Section "Screen"
Identifier "Screen1"
Monitor "ExtMonitor"
Device "Card1"
Defaultdepth 24
EndSection
#Section "ServerLayout"
# Identifier "Default Layout"
# screen "Default Screen"
# Inputdevice "Synaptics Touchpad"
#EndSection
# added
Section "ServerLayout"
Identifier "DualHead"
screen "Default Screen" 0 0
screen "Screen1" RightOf "Default Screen"
Inputdevice "Synaptics Touchpad"
EndSection
＃如果只是擴展屏幕，也就是窗口可以拖到另外一個屏幕，就加上下面這段；如果需要兩個獨立的顯示就去掉。
# added
Section "ServerFlags"
Option "Xinerama" "true"
EndSection