I use a Pioneer notebook fitted with a Nvidia Geforce 8600M GS graphics card. This Geforce card has a DVI output and in the office, and at home, I use twin screen settings in the Nvidia X Server Settings to output to both the notebook screen as the primary screen and to a 19" widescreen monitor as the secondary screen. This set up is handy for referring to one window while working on another for instance with both windows maximised.

The problem I ran into recently with this set up was if the notebook booted up on battery power the graphics were reduced to very low resolution as the power connector check was failing.

The line I needed to add to /etc/X11/xorg.conf in the "screen" sections which resolved the problem was;

    Option        "NoPowerConnectorCheck" "1"

My xorg.conf that now works for this combination is;
# nvidia-xconfig: X configuration file generated by nvidia-xconfig
# nvidia-xconfig:  version 1.0  (buildmeister@builder63)  Mon Mar 23 15:33:27 PST 2009

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
EndSection

Section "Files"
EndSection

Section "Module"
    Load           "dbe"
    Load           "extmod"
    Load           "type1"
    Load           "freetype"
    Load           "glx"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/psaux"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Unknown"
    HorizSync       28.0 - 33.0
    VertRefresh     43.0 - 72.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Option        "NoPowerConnectorCheck" "1"
    Monitor        "Monitor0"
    DefaultDepth    24
    SubSection     "Display"
    Depth       24
    EndSubSection
EndSection

  These settings are working well. The notebook will boot on battery power with the full screen resolution. Enabling TwinView is possible by following System>Administration>NVIDIA X Server Settings then select the display to be enabled >Configure>TwinView>Apply>Yes(Do you want to keep these settings) >Quit

This way my xorg.conf has the standard settings to boot with just the laptop display on battery power and skip the power connector check.