J'ai lu les differents post sur le sujet et j'ai ete amene a essaye:
xvidtune (g rien compris et marche pas)
edit du xf86config4 le voici et ca me donne rien :
 
*********************************************************
Section "Files"
    # Multiple FontPath entries are allowed (they are concatenated together)
    # By default, Mandrake 6.0 and later now use a font server independent of
    # the X server to render fonts.
    FontPath "unix/:-1"
EndSection
 
Section "ServerFlags"
    #DontZap # disable <Crtl><Alt><BS> (server abort)
    #DontZoom # disable <Crtl><Alt><KP_+>/<KP_-> (resolution switching)
    AllowMouseOpenFail # allows the server to start up even if the mouse doesn't work
EndSection
 
Section "Module"
    Load "dbe" # Double-Buffering Extension
    Load "v4l" # Video for Linux
    Load "extmod"
    Load "type1"
    Load "freetype"
    Load "glx" # 3D layer
EndSection
 
Section "InputDevice"
    Identifier "Keyboard1"
    Driver "Keyboard"
    Option "XkbModel" "pc105"
    Option "XkbLayout" "fr"
    Option "XkbOptions" ""
EndSection
 
Section "InputDevice"
    Identifier "Mouse1"
    Driver "mouse"
    Option "Protocol" "ExplorerPS/2"
    Option "Device" "/dev/usbmouse"
    Option "ZAxisMapping" "6 7"
EndSection
 
Section "Monitor"
    Identifier "monitor1"
    VendorName "Mitsubishi"
    ModelName "Mitsubishi Diamond Plus 91 (NFL9905)"
    HorizSync 30.0-96.0
    VertRefresh 50.0-140.0
    ModeLine "640x480"   65.22  640  672  832  896 480 482 494  520
    ModeLine "800x600"  100.35  800  840 1040 1120 600 602 614  640
    ModeLine "1024x768" 134.24 1024 1072 1312 1408 768 770 782  808
    ModeLine "1152x864" 147.18 1152 1200 1440 1536 864 866 878  904
    ModeLine "1280x960" 165.88 1280 1336 1616 1728 960 962 974 1000
EndSection
 
Section "Device"
    Identifier "device1"
    VendorName "NVidia"
    BoardName "NVIDIA GeForce (fbdev)"
    Driver "fbdev"
    Option "DPMS"
EndSection
 
Section "Screen"
    Identifier "screen1"
    Device "device1"
    Monitor "monitor1"
    DefaultColorDepth 16
     
    Subsection "Display"
        Depth 8
        Modes "1280x960"
    EndSubsection
     
    Subsection "Display"
        Depth 15
        Modes "1280x960"
    EndSubsection
     
    Subsection "Display"
        Depth 16
        Modes "1280x960"
    EndSubsection
     
    Subsection "Display"
        Depth 24
        Modes "1280x960"
    EndSubsection
EndSection
 
Section "ServerLayout"
    Identifier "layout1"
    InputDevice "Keyboard1" "CoreKeyboard"
    InputDevice "Mouse1" "CorePointer"
    Screen "screen1"
EndSection
 
J'attends vos suggestion avec impatience car c trop moche le 60hz

xfree en frame buffer avec une carte nvidia, tu as pas honte ???
 
commences par installer les drivers nvidia et a degager tes modelines inutiles
 
et pis le 24bit par defaut, ca rame pas