A configuração seguinte funcionou para mim com dois Dell U2312HM, quando eu estava usando o Nvidia TwinView, mas não copie & amp; colar.
# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings: version 1.0 (buildd@yellow) Fri Apr 9 11:51:21 UTC 2010
Section "ServerLayout"
Identifier "Layout0"
Screen 0 "Screen0" 0 0
# InputDevice "Keyboard0" "CoreKeyboard"
# InputDevice "Mouse0" "CorePointer"
Option "Xinerama" "0"
EndSection
Section "Files"
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"
# HorizSync source: edid, VertRefresh source: edid
Identifier "Monitor0"
VendorName "DELL"
ModelName "DELL U2312HM"
HorizSync 30.0 - 83.0
VertRefresh 56.0 - 76.0
Option "DPMS"
EndSection
Section "Device"
Identifier "Device0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce 210"
EndSection
Section "Screen"
Identifier "Screen0"
Device "Device0"
Monitor "Monitor0"
DefaultDepth 24
Option "TwinView" "1"
Option "TwinViewXineramaInfoOrder" "DFP-0"
Option "metamodes" "DFP-0: 1920x1080_60 +0+0, DFP-1: 1920x1080_60 +1920+0"
SubSection "Display"
Depth 24
EndSubSection
EndSection