How can I run two screens from two separate GPUs?

I have two nVidia GTS 450 GPUs, each with a DVI, an HDMI and a VGA port. I want two screens, both running off the DVI ports.

I've setup my xorg.conf file in /etc/X11/xorg.conf but it is not working.

xorg.conf

# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings: version 361.42 (buildd@lgw01-18) Tue Apr 5 14:33:28 UTC 2016
Section "ServerLayout" Identifier "Layout0" Screen 0 "Screen0" 0 0 InputDevice "Keyboard0" "CoreKeyboard" InputDevice "Mouse0" "CorePointer" Option "Xinerama" "0"
EndSection
Section "Files"
EndSection
Section "Module" Load "dbe" Load "extmod" Load "type1" Load "freetype" Load "glx"
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 "Acer S220HQL" HorizSync 31.0 - 83.0 VertRefresh 56.0 - 76.0 Option "DPMS"
EndSection
Section "Device" Identifier "Device0" Driver "nvidia" VendorName "NVIDIA Corporation" BoardName "GeForce GTS 450" BusID "PCI:1:0:0"
EndSection
Section "Screen" Identifier "Screen0" Device "Device0" Monitor "Monitor0" DefaultDepth 24 Option "Stereo" "0" Option "nvidiaXineramaInfoOrder" "DFP-0" Option "metamodes" "GPU-661ea8ef-0beb-0b79-5958-62e5a84fb2f5.DVI-I-1: nvidia-auto-select +0+0, GPU-93c7ee63-95cd-dd42-a64e-d669451a0150.DVI-I-1: nvidia-auto-select +1920+0" Option "MultiGPU" "Off" Option "SLI" "off" Option "BaseMosaic" "on" SubSection "Display" Depth 24 EndSubSection
EndSection

It would appear that nVidia is ignoring my xorg file - as when I open the X Server settings program, I see the following:

Base mosaic turns itself off, and the second screen is disabled.

I'm running Ubuntu GNOME 16.04 and I have nVidia drivers installed, version 361-updates.

How can I get nVidia to recognise my xorg.conf file, and to have two screens on two cards?

1 Answer

So uhh... This is a little embarrassing... I uhh my umm. Okay. I'll say it. My SLI cord came undone.

I have got it working now. Although I also had to change my xorg file from using DPF-0 screen to DVI-I-0.

Yep.