Here you can see my xorg.conf configured with my ati radeon 9200 (rv280) and my Acer monitor AL1715

# /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"
EndSection

Section "Extensions"
        Option "RENDER" "Enable"
EndSection

Section "DRI"
	Mode	0666
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"
  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. RV280 [Radeon 9200 PRO]"
	Driver		"radeon"
	BusID		"PCI:1:0:0"
#	Option		"XAANoOffscreenPixmaps"			# Faster RENDER acceleration			###
#	VideoRam   131072			# 128 MB VRAM							###
	Option		"AccelMethod"		"XAA"   	# Use XFree86 Acceleration Architecture  	#
	Option		"AccelDFS"		"0" 		# pour ATI 9250
	Option		"AGPMode"		"8"     	# AGP- 8 fonctionne mois bien
	Option		"AGPSize"		  "128"    	# AGP aperture size - 128 fonctionne moins bien
	Option		"GARTSize"		  "64"		# TEST
	Option		"RingSize"		   "8"
	Option		"BufferSize"		   "2"
	Option		"EnablePageFlip"      "1"		# Enable page flipping for 3D apps
	Option		"ColorTiling"		   "1"
	Option		"EnableDepthMoves"	"yes"
	Option		"UseFBDev"     		"false"
	Option		"RenderAccel"   	"true"  	# Enable the hardware render acceleration
	Option		"mtrr"			       "on"
	Option 		"SubPixelOrder" 	"none"
	Option 		"DynamicClocks"       "on"
#	Option		"BackingStore"  	"true"		# Faster double buffering			###
	Option		"DPMS"
	Option		"DRI"			"true"
EndSection

Section "Monitor"
	Identifier	"AL1715"
	Option		"DPMS"
EndSection

Section "Screen"
	Identifier	"Default Screen"
	Device		"ATI Technologies, Inc. RV280 [Radeon 9200 PRO]"
	Monitor		"AL1715"
	DefaultDepth	24
	SubSection "Display"
		Depth		1
		Modes		"1280x1024" "1024x768" "832x624" "800x600" "720x400" "640x480"
	EndSubSection
	SubSection "Display"
		Depth		4
		Modes		"1280x1024" "1024x768" "832x624" "800x600" "720x400" "640x480"
	EndSubSection
	SubSection "Display"
		Depth		8
		Modes		"1280x1024" "1024x768" "832x624" "800x600" "720x400" "640x480"
	EndSubSection
	SubSection "Display"
		Depth		15
		Modes		"1280x1024" "1024x768" "832x624" "800x600" "720x400" "640x480"
	EndSubSection
	SubSection "Display"
		Depth		16
		Modes		"1280x1024" "1024x768" "832x624" "800x600" "720x400" "640x480"
	EndSubSection
	SubSection "Display"
		Depth		24
		Modes		"1280x1024" "1024x768" "832x624" "800x600" "720x400" "640x480"
	EndSubSection

	Option    "AddARGBGLXVisuals"    "True"
	Option "DisableGLXRootClipping" "True"
EndSection

Section "ServerLayout"
	Identifier	"Default Layout"
	Screen		"Default Screen"
	InputDevice	"Generic Keyboard"
	InputDevice	"Configured Mouse"
	InputDevice     "stylus" "SendCoreEvents"
	InputDevice     "cursor" "SendCoreEvents"
	InputDevice     "eraser" "SendCoreEvents"
	
	option "offtime" "30" 
	Option "AIGLX" "true"		 # Nécessaire pour beryl
EndSection