questo è il mio xorg.conf (ho solo eliminato delle modeline perchè era troppo lungo ...)

Section "ServerLayout"
Identifier "XFree86 Configured"
Screen 0 "Screen0" 0 0
InputDevice "Keyboard0" "CoreKeyboard"
# PS/2 Mouse not detected
# Serial Mouse not detected
InputDevice "USB Mouse" "CorePointer"
EndSection

Section "ServerFlags"
Option "AllowMouseOpenFail" "true"

EndSection

Section "Files"
RgbPath "/usr/share/X11/rgb"
ModulePath "/usr/lib/xorg/modules"
FontPath "/usr/share/fonts/X11/misc:unscaled"
FontPath "/usr/share/fonts/X11/75dpi:unscaled"
FontPath "/usr/share/fonts/X11/100dpi:unscaled"
FontPath "/usr/share/fonts/X11/Type1"
FontPath "/usr/share/fonts/X11/Speedo"
FontPath "/usr/share/fonts/X11/PEX"
# Additional fonts: Locale, Gimp, TTF...
FontPath "/usr/share/fonts/X11/cyrillic"
# FontPath "/usr/share/fonts/X11/latin2/75dpi"
# FontPath "/usr/share/fonts/X11/latin2/100dpi"
# True type and type1 fonts are also handled via xftlib, see /etc/X11/XftConfig!
FontPath "/var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType"
FontPath "/usr/share/fonts/truetype"
FontPath "/usr/share/fonts/latex-ttf-fonts"
EndSection

Section "Module"
# Comments: see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=346408
Load "dbe" # Double Buffering Extension, very important.
Load "dri" # This shouldn't be available choice if user has selected driver vga, vesa or nv.
Load "glx" # GLX Extension.
Load "freetype" # Freetype fonts.
Load "type1" # Type 1 fonts
Load "record" # Developer extension, usually not needed
# Load "extmod" # This is okay, but if you look into "man xorg.conf" you'll find option NOT to include DGA extension with extmod, and for a good reason.. DGA causes instability as it access videoram without consulting X about it.
SubSection "extmod"
Option "omit xfree86-dga"
EndSubSection
# Load "speedo" # Speedo fonts, this module doesn't exist in Xorg 7.0.17
# The following are deprecated/unstable/unneeded in Xorg 7.0
# Load "ddc" # ddc probing of monitor, this should be never present, as it gets automatically loaded.
# Load "GLcore" # This should be never present, as it gets automatically loaded.
# Load "bitmap" # Should be never present, as it gets automatically loaded. This is a font module, and loading it in xorg.conf makes X try to load it twice.
EndSection

Section "InputDevice"
Identifier "Keyboard0"
Driver "kbd"
Option "CoreKeyboard"
Option "XkbRules" "xorg"
Option "XkbModel" "pc105"
Option "XkbLayout" "it"

EndSection

Section "InputDevice"
Identifier "Serial Mouse"
Driver "mouse"
Option "Protocol" "Microsoft"
Option "Device" "/dev/ttyS0"
Option "Emulate3Buttons" "true"
Option "Emulate3Timeout" "70"
Option "SendCoreEvents" "true"
EndSection

Section "InputDevice"
Identifier "PS/2 Mouse"
Driver "mouse"
Option "Protocol" "auto"
Option "ZAxisMapping" "4 5"
Option "Device" "/dev/psaux"
Option "Emulate3Buttons" "true"
Option "Emulate3Timeout" "70"
Option "SendCoreEvents" "true"
EndSection

Section "InputDevice"
Identifier "USB Mouse"
Driver "mouse"
Option "Device" "/dev/input/mice"
Option "SendCoreEvents" "true"
Option "Protocol" "IMPS/2"
Option "ZAxisMapping" "4 5"
Option "Buttons" "5"
EndSection

# Auto-generated by KNOPPIX mkxf86config

Section "Monitor"
Identifier "Monitor0"
Option "DPMS" "true"
# HorizSync 28.0 - 78.0 # Warning: This may fry very old Monitors
HorizSync 28.0 - 96.0 # Warning: This may fry old Monitors
VertRefresh 50.0 - 75.0 # Very conservative. May flicker.
# VertRefresh 50.0 - 62.0 # Extreme conservative. Will flicker. TFT default.
# Default modes distilled from
# "VESA and Industry Standards and Guide for Computer Display Monitor
# Timing", version 1.0, revision 0.8, adopted September 17, 1998.
# $XFree86: xc/programs/Xserver/hw/xfree86/etc/vesamodes,v 1.4 1999/11/18 16:52:17 tsi Exp $
# 640x350 @ 85Hz (VESA) hsync: 37.9kHz
ModeLine "640x350" 31.5 640 672 736 832 350 382 385 445 +hsync -vsync
# 640x400 @ 85Hz (VESA) hsync: 37.9kHz
ModeLine "640x400" 31.5 640 672 736 832 400 401 404 445 -hsync +vsync
# 720x400 @ 85Hz (VESA) hsync: 37.9kHz
ModeLine "720x400" 35.5 720 756 828 936 400 401 404 446 -hsync +vsync
# 640x480 @ 60Hz (Industry standard) hsync: 31.5kHz
ModeLine "640x480" 25.2 640 656 752 800 480 490 492 525 -hsync -vsync
# 640x480 @ 72Hz (VESA) hsync: 37.9kHz
ModeLine "640x480" 31.5 640 664 704 832 480 489 491 520 -hsync -vsync
# 640x480 @ 75Hz (VESA) hsync: 37.5kHz
ModeLine "640x480" 31.5 640 656 720 840 480 481 484 500 -hsync -vsync
# 640x480 @ 85Hz (VESA) hsync: 43.3kHz
ModeLine "640x480" 36.0 640 696 752 832 480 481 484 509 -hsync -vsync
# 800x600 @ 56Hz (VESA) hsync: 35.2kHz
ModeLine "800x600" 36.0 800 824 896 1024 600 601 603 625 +hsync +vsync
# 800x600 @ 60Hz (VESA) hsync: 37.9kHz
ModeLine "800x600" 40.0 800 840 968 1056 600 601 605 628 +hsync +vsync
# 800x600 @ 72Hz (VESA) hsync: 48.1kHz
ModeLine "800x600" 50.0 800 856 976 1040 600 637 643 666 +hsync +vsync
# 800x600 @ 75Hz (VESA) hsync: 46.9kHz
ModeLine "800x600" 49.5 800 816 896 1056 600 601 604 625 +hsync +vsync
# 800x600 @ 85Hz (VESA) hsync: 53.7kHz
ModeLine "800x600" 56.3 800 832 896 1048 600 601 604 631 +hsync +vsync
# 1024x768i @ 43Hz (industry standard) hsync: 35.5kHz
ModeLine "1024x768" 44.9 1024 1032 1208 1264 768 768 776 817 +hsync +vsync Interlace
# 1024x768 @ 60Hz (VESA) hsync: 48.4kHz
ModeLine "1024x768" 65.0 1024 1048 1184 1344 768 771 777 806 -hsync -vsync
# 1024x768 @ 70Hz (VESA) hsync: 56.5kHz
ModeLine "1024x768" 75.0 1024 1048 1184 1328 768 771 777 806 -hsync -vsync
# 1024x768 @ 75Hz (VESA) hsync: 60.0kHz
ModeLine "1024x768" 78.8 1024 1040 1136 1312 768 769 772 800 +hsync +vsync
# 1024x768 @ 85Hz (VESA) hsync: 68.7kHz
ModeLine "1024x768" 94.5 1024 1072 1168 1376 768 769 772 808 +hsync +vsync
# 1152x864 @ 75Hz (VESA) hsync: 67.5kHz
ModeLine "1152x864" 108.0 1152 1216 1344 1600 864 865 868 900 +hsync +vsync
# 1280x960 @ 60Hz (VESA) hsync: 60.0kHz
ModeLine "1280x960" 108.0 1280 1376 1488 1800 960 961 964 1000 +hsync +vsync
# 1280x960 @ 85Hz (VESA) hsync: 85.9kHz
ModeLine "1280x960" 148.5 1280 1344 1504 1728 960 961 964 1011 +hsync +vsync
# 1280x1024 @ 60Hz (VESA) hsync: 64.0kHz
ModeLine "1280x1024" 108.0 1280 1328 1440 1688 1024 1025 1028 1066 +hsync +vsync
# 1280x1024 @ 75Hz (VESA) hsync: 80.0kHz
ModeLine "1280x1024" 135.0 1280 1296 1440 1688 1024 1025 1028 1066 +hsync +vsync
# 1280x1024 @ 85Hz (VESA) hsync: 91.1kHz
# ModeLine "1280x1024" 157.5 1280 1344 1504 1728 1024 1025 1028 1072 +hsync +vsync
Modeline "1280x1024" 157.50 1280 1328 1488 1728 1024 1025 1028 1072 +hsync +vsync
# 1600x1200 @ 60Hz (VESA) hsync: 75.0kHz
ModeLine "1600x1200" 162.0 1600 1664 1856 2160 1200 1201 1204 1250 +hsync +vsync
# 1600x1200 @ 65Hz (VESA) hsync: 81.3kHz
ModeLine "1600x1200" 175.5 1600 1664 1856 2160 1200 1201 1204 1250 +hsync +vsync
# 1600x1200 @ 70Hz (VESA) hsync: 87.5kHz
ModeLine "1600x1200" 189.0 1600 1664 1856 2160 1200 1201 1204 1250 +hsync +vsync
# 1600x1200 @ 75Hz (VESA) hsync: 93.8kHz
ModeLine "1600x1200" 202.5 1600 1664 1856 2160 1200 1201 1204 1250 +hsync +vsync
# 1600x1200 @ 85Hz (VESA) hsync: 106.3kHz
ModeLine "1600x1200" 229.5 1600 1664 1856 2160 1200 1201 1204 1250 +hsync +vsync
# 1792x1344 @ 60Hz (VESA) hsync: 83.6kHz
ModeLine "1792x1344" 204.8 1792 1920 2120 2448 1344 1345 1348 1394 -hsync +vsync
# 1792x1344 @ 75Hz (VESA) hsync: 106.3kHz
ModeLine "1792x1344" 261.0 1792 1888 2104 2456 1344 1345 1348 1417 -hsync +vsync
# 1856x1392 @ 60Hz (VESA) hsync: 86.3kHz
ModeLine "1856x1392" 218.3 1856 1952 2176 2528 1392 1393 1396 1439 -hsync +vsync
# 1856x1392 @ 75Hz (VESA) hsync: 112.5kHz
ModeLine "1856x1392" 288.0 1856 1984 2208 2560 1392 1393 1396 1500 -hsync +vsync
# 1920x1440 @ 60Hz (VESA) hsync: 90.0kHz
ModeLine "1920x1440" 234.0 1920 2048 2256 2600 1440 1441 1444 1500 -hsync +vsync
# 1920x1440 @ 75Hz (VESA) hsync: 112.5kHz
ModeLine "1920x1440" 297.0 1920 2064 2288 2640 1440 1441 1444 1500 -hsync +vsync

EndSection

Section "Device"
### Available Driver options are:-
# sw_cursor is needed for some ati and radeon cards
Option "sw_cursor"
#Option "hw_cursor"
#Option "NoAccel"
#Option "ShowCache"
#Option "ShadowFB"
#Option "UseFBDev"
#Option "Rotate"
Identifier "Card0"
# The following line is auto-generated by KNOPPIX mkxf86config
Driver "ati"
VendorName "All"
BoardName "All"
# BusID "PCI:1:0:0"
EndSection

Section "Screen"
Identifier "Screen0"
Device "Card0"
Monitor "Monitor0"
DefaultColorDepth 16
SubSection "Display"
Depth 1
Modes "1024x768" "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 4
Modes "1024x768" "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 8
Modes "1024x768" "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 15
Modes "1024x768" "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 16
Modes "1024x768" "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 24
Modes "1024x768" "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 32
Modes "1024x768" "800x600" "640x480"
EndSubSection
EndSection

Section "DRI"
Mode 0666
EndSection