ftp://download.nvidia.com/XFree86/Linux-x...7174/README.txt
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Option "ConnectedMonitor" "string"
Allows you to override what the NVIDIA kernel module
detects is connected to your video card. This may
be useful, for example, if you use a KVM (keyboard,
video, mouse) switch and you are switched away when
X is started. In such a situation, the NVIDIA kernel
module cannot detect what display devices are connected,
and the NVIDIA X driver assumes you have a single CRT.
Valid values for this option are "CRT" (cathode ray
tube), "DFP" (digital flat panel), or "TV" (television);
if using TwinView, this option may be a comma-separated
list of display devices; e.g.: "CRT, CRT" or "CRT, DFP".
NOTE: anything attached to a 15 pin VGA connector is
regarded by the driver as a CRT. "DFP" should only be
used to refer to flatpanels connected via a DVI port.