It took ages to get my multi-head graphics card working on my new Linux distro. It supports three monitors, but I’m only using two. I’m using Ubunto Breezy Badger (5.10). I didn’t have to recompile the kernel. I’m using the latest driver from Matrox themselves (although there are also unofficial ones). I hope that the following may be of use to others trying to do the same thing.

Here is my xorg.conf file

# /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/CID"
        FontPath        "/usr/share/X11/fonts/100dpi"
        FontPath        "/usr/share/X11/fonts/75dpi"
        # paths to defoma fonts
        FontPath        "/var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType"
        FontPath        "/var/lib/defoma/x-ttcidfont-conf.d/dirs/CID"
EndSection

Section "Module"
        Load    "GLcore"
        Load    "i2c"
        Load    "bitmap"
        Load    "ddc"
        Load    "dri"
        Load    "extmod"
        Load    "freetype"
        Load    "glx"
        Load    "int10"
        Load    "type1"
        Load    "vbe"
EndSection

# Enable multi-head support (Xinerama)
Section "ServerFlags"
        Option "Xinerama" "true"
EndSection

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

Section "InputDevice"
        Identifier      "Configured Mouse"
        Driver          "mouse"
        Option          "CorePointer"
        Option          "Device"                "/dev/input/mice"
        Option          "Protocol"              "ImPS/2"
        Option          "Emulate3Buttons"       "true"
        Option          "ZAxisMapping"          "4 5"
EndSection

Section "Device"
Identifier "Matrox P750 1"
Driver "mtx"
BusID "PCI:1:0:0"
Screen 0
EndSection

Section "Device"
Identifier "Matrox P750 2"
Driver "mtx"
BusID "PCI:1:0:0"
Screen 1
EndSection

# HorizSync is given in kHz
# VertRefresh is given in Hz
Section "Monitor"
        Identifier      "Iiyama 17"
        Option          "DPMS"
        HorizSync       60-86
        VertRefresh     60-85
EndSection

Section "Monitor"
        Identifier      "Generic 15"
        Option          "DPMS"
        HorizSync       28-64
        VertRefresh     43-60
EndSection

Section "Screen"
        Identifier "Screen0"
        Device "Matrox P750 1"
        Monitor "Iiyama 17"
        DefaultDepth 24
        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
EndSection

Section "Screen"
        Identifier "Screen1"
        Device "Matrox P750 2"
        Monitor "Generic 15"
        DefaultDepth 24
        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
EndSection

Section "ServerLayout"
        Identifier      "Default Layout"
        Screen 0 "Screen0" LeftOf "Screen1"
        Screen 1 "Screen1" 0 0
        InputDevice     "Generic Keyboard"
        InputDevice     "Configured Mouse"

        Option "Xinerama" "on"
EndSection

Section "DRI"
        Mode    0666
EndSection