xinerama-config funktioniert nicht

[t0bias]

hi,

ich versuche eine xinerama-konfiguration hinzubekommen.
habe eine
Matrox Graphics, Inc. MGA G550 AGP
Karte und zwei identische IBM-TFT's angeschlossen.
Xinerama ist installiert und der Kernel auch entsprechend
für Dual-Head-Betrieb konfiguriert.
Trotzdem geben beide Bildschirme zweimal einen normalen
Bildschirmoutput, sprich ich habe den Desktop doppelt, anstatt
einen grossen, über 2 Bildschirme erstreckten.
meine xorg.conf:

# Xorg.blablabla

Section "Files"
        FontPath        "/usr/share/fonts/X11/misc"
        FontPath        "/usr/X11R6/lib/X11/fonts/misc"
        FontPath        "/usr/share/fonts/X11/cyrillic"
        FontPath        "/usr/X11R6/lib/X11/fonts/cyrillic"
        FontPath        "/usr/share/fonts/X11/100dpi/:unscaled"
        FontPath        "/usr/X11R6/lib/X11/fonts/100dpi/:unscaled"
        FontPath        "/usr/share/fonts/X11/75dpi/:unscaled"
        FontPath        "/usr/X11R6/lib/X11/fonts/75dpi/:unscaled"
        FontPath        "/usr/share/fonts/X11/Type1"
        FontPath        "/usr/X11R6/lib/X11/fonts/Type1"
        FontPath        "/usr/share/fonts/X11/100dpi"
        FontPath        "/usr/X11R6/lib/X11/fonts/100dpi"
        FontPath        "/usr/share/fonts/X11/75dpi"
        FontPath        "/usr/X11R6/lib/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    "vbe"
EndSection

Section "InputDevice"
        Identifier      "Generic Keyboard"
        Driver          "kbd"
        Option          "CoreKeyboard"
        Option          "XkbRules"      "xorg"
        Option          "XkbModel"      "pc105"
        Option          "XkbLayout"     "ch"
        Option          "XkbVariant"    "de"
EndSection

Section "InputDevice"
        Identifier      "Configured Mouse"
        Driver          "mouse"
        Option          "CorePointer"
        Option          "Device"                "/dev/input/mice"
        Option          "Protocol"              "ImPS/2"
        Option          "Emulate3Buttons"       "true"
EndSection

Section "Device"
        Identifier      "Matrox Graphics, Inc. MGA G550 AGP 0"
        Driver          "mga"
        BusID           "PCI:1:0:0"
EndSection

Section "Device"
        Identifier      "Matrox Graphics, Inc. MGA G550 AGP 1"
        Driver          "mga"
        BusID           "PCI:1:0:0"
EndSection


Section "Monitor"
        Identifier      "IBM 9511 T54 0"
        Option          "DPMS"
        HorizSync       28-51
        VertRefresh     43-60
EndSection

Section "Monitor"
        Identifier      "IBM 9511 T54 1"
        Option          "DPMS"
        HorizSync       28-51
        VertRefresh     43-60
EndSection

Section "Screen"
        Identifier      "Default Screen 0"
        Device          "Matrox Graphics, Inc. MGA G550 AGP 0"
        Monitor         "IBM 9511 T54 0"
        DefaultDepth    16
        SubSection "Display"
                Depth           16
                Modes           "1024x768" "800x600" "640x480"
        EndSubSection
EndSection

Section "Screen"
        Identifier      "Default Screen 1"
        Device          "Matrox Graphics, Inc. MGA G550 AGP 1"
        Monitor         "IBM 9511 T54 1"
        DefaultDepth    16
        SubSection "Display"
                Depth           16
                Modes           "1024x768" "800x600" "640x480"
        EndSubSection
EndSection

Section "ServerLayout"
    Identifier "Multihead"
    Screen "Default Screen 0"
    Screen "Default Screen 1" LeftOf  "Default Screen 0"
    InputDevice     "mouse1" "CorePointer"
    InputDevice     "keyboard1" "CoreKeyboard"
    Option "Xinerama"
EndSection

Section "DRI"
        Mode    0666
EndSection

wer weiss weiter?

gruss

t0bi