Eu poderia fazer isso. Eu tenho uma placa ATI onboard (HD 3200) e uma placa Nvidia PCI-E (8600GT). Eu saída dois monitores da placa Nvidia (DVI- > VGA) e um a bordo.
O desempenho não é tão bom. Às vezes eu tive falhas quando (acidentalmente) movendo vídeos de uma das telas da Nvidia para a ATI. Além disso, o glxgears não produz nada no monitor da ATI. Mas para o material básico padrão de desktop, ele funciona muito bem.
Aqui está o meu arquivo xorg.conf, espero que seja útil para você.
Section "ServerLayout"
Identifier "Layout0"
Screen 0 "Screen0" 1360 0
Screen 1 "Screen2" LeftOf "Screen0"
Screen 2 "Screen1" RightOf "Screen0"
InputDevice "Keyboard0" "CoreKeyboard"
InputDevice "Mouse0" "CorePointer"
Option "Xinerama" "1"
EndSection
Section "Module"
Load "glx"
EndSection
Section "InputDevice"
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"
Identifier "Monitor0"
VendorName "Unknown"
ModelName "Samsung SyncMaster"
HorizSync 30.0 - 61.0
VertRefresh 56.0 - 75.0
Option "DPMS"
EndSection
Section "Monitor"
Identifier "Monitor1"
VendorName "Unknown"
ModelName "Philips"
HorizSync 14.0 - 70.0
VertRefresh 56.0 - 85.0
Option "DPMS"
# HorizSync source: edid, VertRefresh source: edid
EndSection
Section "Monitor"
Identifier "Monitor2"
VendorName "Unknown"
ModelName "LG Flatron L177WS"
HorizSync 31.5 - 50.0
VertRefresh 40.0 - 90.0
Option "DPMS"
EndSection
Section "Device"
Identifier "Device0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce 8600 GT"
BusID "PCI:02:00:00"
Screen 0
EndSection
Section "Device"
Identifier "Device1"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce 8600 GT"
BusID "PCI:02:00:00"
Screen 1
EndSection
Section "Device"
Identifier "Device2"
Driver "radeon"
VendorName "ATI"
BoardName "ATI Radeon HD3200"
BusID "PCI:01:05:00"
Screen 0
EndSection
Section "Screen"
Identifier "Screen0"
Device "Device0"
Monitor "Monitor0"
DefaultDepth 24
Option "TwinView" "0"
Option "metamodes" "CRT-1: 1360x768_60 +0+0; CRT-1: 1360x768 +0+0"
SubSection "Display"
Depth 24
EndSubSection
EndSection
Section "Screen"
Identifier "Screen1"
Device "Device1"
Monitor "Monitor1"
DefaultDepth 24
Option "TwinView" "0"
Option "metamodes" "CRT-0: nvidia-auto-select +0+0"
SubSection "Display"
Depth 24
EndSubSection
EndSection
Section "Screen"
Identifier "Screen2"
Device "Device2"
Monitor "Monitor2"
DefaultDepth 24
SubSection "Display"
Modes "1280x640"
Depth 24
EndSubSection
EndSection
Section "Extensions"
Option "Composite" "Disable"
EndSection