You can use the CustomEDID
X driver option (see e.g. http://us.download.nvidia.com/freebs...pendix-f.html)
. You can save the display's EDID using `nvidia-settings`
using the 'Acquire EDID...'
button on the display's information page. Please be sure to update the EDID's checksum after modifying it or the NVIDIA X driver will reject it.