xorg.conf

Section "ServerLayout"
	Identifier     "X.org Configured"
	Screen      0  "Screen0" 0 0
	Screen      1  "Screen1" LeftOf "Screen0"
EndSection

Section "Monitor"
	Identifier   "Monitor0"
EndSection

Section "Monitor"
	Identifier   "Monitor1"
EndSection

Section "Device"
        ### Available Driver options are:-
        ### Values: <i>: integer, <f>: float, <bool>: "True"/"False",
        ### <string>: "String", <freq>: "<f> Hz/kHz/MHz",
        ### <percent>: "<f>%"
        ### [arg]: arg optional
        #Option     "Accel"              	# [<bool>]
        #Option     "SWcursor"           	# [<bool>]
        #Option     "EnablePageFlip"     	# [<bool>]
        #Option     "ColorTiling"        	# [<bool>]
        #Option     "ColorTiling2D"      	# [<bool>]
        #Option     "RenderAccel"        	# [<bool>]
        #Option     "SubPixelOrder"      	# [<str>]
        #Option     "AccelMethod"        	# <str>
        #Option     "EXAVSync"           	# [<bool>]
        #Option     "EXAPixmaps"         	# [<bool>]
        #Option     "ZaphodHeads"        	# <str>
        #Option     "EnablePageFlip"     	# [<bool>]
        #Option     "SwapbuffersWait"    	# [<bool>]
	Identifier  "Card0"
	Driver      "radeon"
	BusID       "PCI:1:0:0"
EndSection

Section "Device"
        ### Available Driver options are:-
        ### Values: <i>: integer, <f>: float, <bool>: "True"/"False",
        ### <string>: "String", <freq>: "<f> Hz/kHz/MHz",
        ### <percent>: "<f>%"
        ### [arg]: arg optional
        #Option     "Accel"              	# [<bool>]
        #Option     "SWcursor"           	# [<bool>]
        #Option     "EnablePageFlip"     	# [<bool>]
        #Option     "ColorTiling"        	# [<bool>]
        #Option     "ColorTiling2D"      	# [<bool>]
        #Option     "RenderAccel"        	# [<bool>]
        #Option     "SubPixelOrder"      	# [<str>]
        #Option     "AccelMethod"        	# <str>
        #Option     "EXAVSync"           	# [<bool>]
        #Option     "EXAPixmaps"         	# [<bool>]
        #Option     "ZaphodHeads"        	# <str>
        #Option     "EnablePageFlip"     	# [<bool>]
        #Option     "SwapbuffersWait"    	# [<bool>]
	Identifier  "Card1"
	Driver      "radeon"
	BusID       "PCI:3:0:0"
EndSection

Section "Screen"
	Identifier "Screen0"
	Device     "Card0"
	Monitor    "Monitor0"
EndSection

Section "Screen"
	Identifier "Screen1"
	Device     "Card1"
	Monitor    "Monitor1"
EndSection