Aqui está minha tela atualizada do Xorg.conf (sem Xinerama):
# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings: version 340.46 (pbuilder@zam904) Fri Oct 17 21:29:34 UTC 2014
Section "ServerLayout"
Identifier "Layout0"
Screen 0 "Screen0" 0 0
Screen 1 "Screen1" RightOf "Screen0"
Screen 2 "Screen2" 0 1080
Screen 3 "Screen3" RightOf "Screen2"
Screen 4 "Screen4" RightOf "Screen3"
Screen 5 "Screen5" RightOf "Screen4"
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 "Unknown"
ModelName "VIZ E601i-A3E"
HorizSync 31.0 - 70.0
VertRefresh 50.0 - 77.0
Option "DPMS"
Option "DPI" "96x96"
EndSection
Section "Monitor"
# HorizSync source: edid, VertRefresh source: edid
Identifier "Monitor1"
VendorName "Unknown"
ModelName "VIZ E601i-A3E"
HorizSync 31.0 - 70.0
VertRefresh 50.0 - 77.0
Option "DPMS"
Option "DPI" "96x96"
EndSection
Section "Monitor"
# HorizSync source: edid, VertRefresh source: edid
Identifier "Monitor2"
VendorName "Unknown"
ModelName "DELL 1908FP"
HorizSync 31.0 - 83.0
VertRefresh 56.0 - 76.0
Option "DPMS"
EndSection
Section "Monitor"
# HorizSync source: edid, VertRefresh source: edid
Identifier "Monitor3"
VendorName "Unknown"
ModelName "DELL 1905FP"
HorizSync 30.0 - 81.0
VertRefresh 56.0 - 76.0
Option "DPMS"
EndSection
Section "Monitor"
# HorizSync source: edid, VertRefresh source: edid
Identifier "Monitor4"
VendorName "Unknown"
ModelName "DELL 1905FP"
HorizSync 30.0 - 81.0
VertRefresh 56.0 - 76.0
Option "DPMS"
EndSection
Section "Monitor"
# HorizSync source: edid, VertRefresh source: edid
Identifier "Monitor5"
VendorName "Unknown"
ModelName "DELL 1907FPV"
HorizSync 30.0 - 81.0
VertRefresh 56.0 - 76.0
Option "DPMS"
EndSection
Section "Device"
Identifier "Device0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce GTX 275"
BusID "PCI:1:0:0"
Screen 0
EndSection
Section "Device"
Identifier "Device1"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce GTX 275"
BusID "PCI:1:0:0"
Screen 1
EndSection
Section "Device"
Identifier "Device2"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce 8400GS"
BusID "PCI:2:0:0"
Screen 0
EndSection
Section "Device"
Identifier "Device3"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce 8400GS"
BusID "PCI:2:0:0"
Screen 1
EndSection
Section "Device"
Identifier "Device4"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce 8400 GS"
BusID "PCI:3:0:0"
Screen 0
EndSection
Section "Device"
Identifier "Device5"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce 8400 GS"
BusID "PCI:3:0:0"
Screen 1
EndSection
Section "Screen"
Identifier "Screen0"
Device "Device0"
Monitor "Monitor0"
DefaultDepth 24
Option "Stereo" "0"
Option "metamodes" "DVI-I-2: nvidia-auto-select +0+0"
Option "SLI" "Off"
Option "MultiGPU" "Off"
Option "BaseMosaic" "off"
SubSection "Display"
Depth 24
EndSubSection
EndSection
Section "Screen"
Identifier "Screen1"
Device "Device1"
Monitor "Monitor1"
DefaultDepth 24
Option "Stereo" "0"
Option "metamodes" "DVI-I-3: nvidia-auto-select +0+0"
Option "SLI" "Off"
Option "MultiGPU" "Off"
Option "BaseMosaic" "off"
SubSection "Display"
Depth 24
EndSubSection
EndSection
Section "Screen"
Identifier "Screen2"
Device "Device2"
Monitor "Monitor2"
DefaultDepth 24
Option "Stereo" "0"
Option "metamodes" "DVI-I-1: nvidia-auto-select +0+0 {rotation=left}"
Option "SLI" "Off"
Option "MultiGPU" "Off"
Option "BaseMosaic" "off"
SubSection "Display"
Depth 24
EndSubSection
EndSection
Section "Screen"
Identifier "Screen3"
Device "Device3"
Monitor "Monitor3"
DefaultDepth 24
Option "Stereo" "0"
Option "metamodes" "VGA-0: nvidia-auto-select +0+0 {rotation=left}"
Option "SLI" "Off"
Option "MultiGPU" "Off"
Option "BaseMosaic" "off"
SubSection "Display"
Depth 24
EndSubSection
EndSection
Section "Screen"
Identifier "Screen4"
Device "Device4"
Monitor "Monitor4"
DefaultDepth 24
Option "Stereo" "0"
Option "metamodes" "DVI-I-1: nvidia-auto-select +0+0 {rotation=left}"
Option "SLI" "Off"
Option "MultiGPU" "Off"
Option "BaseMosaic" "off"
SubSection "Display"
Depth 24
EndSubSection
EndSection
Section "Screen"
Identifier "Screen5"
Device "Device5"
Monitor "Monitor5"
DefaultDepth 24
Option "Stereo" "0"
Option "metamodes" "VGA-0: nvidia-auto-select +0+0 {rotation=left}"
Option "SLI" "Off"
Option "MultiGPU" "Off"
Option "BaseMosaic" "off"
SubSection "Display"
Depth 24
EndSubSection
EndSection
Com o Xinerma, perco a aceleração e fica em alguns casos, mas é bastante útil.
Acho que finalmente descobri.
Obrigado Dagmar pela sugestão final. Está mais perto de onde eu quero estar, mas ainda não chegou lá.
Status: 90% resolvido.