my xorg.conf, equivalent to the one recommended by the nvidia-drivers-319.17 README (cf. Chapter 18 and 33.)

xorg.conf (text/plain), 835 bytes, created by Victor Mataré on 2013-05-23 01:27:58 UTC

Section "ServerLayout"
    Identifier "layout"
    Screen 0 "nvidia"
    Inactive "modesetting"
EndSection

Section "Device"
    Identifier "nvidia"
    Driver "nvidia"
    BusID "PCI:1:0:0"
EndSection

Section "Screen"
    Identifier "nvidia"
    Device "nvidia"
    # Uncomment this line if your computer has no display devices connected to
    # the NVIDIA GPU.  Leave it commented if you have display devices
    # connected to the NVIDIA GPU that you would like to use.
    Option "UseDisplayDevice" "DP-3, none"
    #Option "UseDisplayDevice" "none"
    Option "TwinView" "1"
EndSection

Section "Device"
    Identifier "modesetting"
    Driver "modesetting"
EndSection

#Section "Device"
#    Identifier "intel"
#    Driver "intel"
#EndSection

Section "Screen"
    Identifier "modesetting"
    Device "modesetting"
EndSection