vesa generic /etc/X11/xorg.conf

Section "Device"
    Identifier    "Configured Video Device"
    Driver        "vesa"
EndSection

Section "Monitor"
    Identifier    "Configured Monitor"
    HorizSync 42.0 - 52.0
    VertRefresh 55.0 - 65.0
    Modeline "1024x768" 60.80  1024 1056 1128 1272   768  768  770  796
    Modeline "800x600" 38.21 800 832 976 1008 600 612 618 631
    Modeline "640x480" 24.11 640 672 760 792 480 490 495 50
EndSection

Section "Screen"
    Identifier    "Default Screen"
    Monitor        "Configured Monitor"
    Device        "Configured Video Device"
    DefaultDepth    24
    Subsection "Display"
        Depth       24
        Modes       "1024x768" "800x600" "640x480"
       EndSubsection
EndSection