I am having some issues getting my third screen working properly.

I had triple screens working fine on 12.04, using 2 nvidia cards. Did a fresh install of 14.04 and having no end of problems getting it working.

It either will just be disabled, or the screen is black with the cursor as an X. I can only enable it from the nvidia server settings tool. The Ubuntu native display settings won't even show the 3rd screen.

I tried copying the xorg.conf from my old install, which upon restarting X worked fine on the login screen, but then it just sat there after I logged in and didn’t do anything (mouse was still working).

I am using gnome-session-fallback instead of unity if that makes any difference. Still having these issues if I try unity though.

How do I get my 3rd screen working and displaying a desktop?

Here is my current xorg.conf

# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings:  version 331.20  (buildd@roseapple)  Mon Feb  3 15:07:22 UTC 2014


Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0" 0 0
    Screen      1  "Screen1" RightOf "Screen0"
    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      "DELL 1907FP"
    HorizSync       30.0 - 81.0
    VertRefresh     56.0 - 76.0
    Option         "DPMS"
EndSection

Section "Monitor"

    # HorizSync source: unknown, VertRefresh source: unknown
    Identifier     "Monitor1"
    VendorName     "Unknown"
    ModelName      "DELL 1907FP"
    HorizSync       0.0 - 0.0
    VertRefresh     0.0
    Option         "DPMS"
EndSection

Section "Monitor"
    Identifier     "Monitor2"
    VendorName     "Unknown"
    ModelName      "DELL 1907FP"
    HorizSync       30.0 - 81.0
    VertRefresh     56.0 - 76.0
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GTX 580"
    BusID          "PCI:1:0:0"
EndSection

Section "Device"
    Identifier     "Device1"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GT 520"
    BusID          "PCI:3:0:0"
EndSection

Section "Device"
    Identifier     "Device2"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GT 520"
    BusID          "PCI:3:0:0"
EndSection

Section "Screen"

# Removed Option "metamodes" "DVI-I-2: nvidia-auto-select +0+0, DVI-I-3: nvidia-auto-select +1280+0"
# Removed Option "metamodes" "DVI-I-2: nvidia-auto-select +0+0"
# Removed Option "SLI" "Off"
# Removed Option "BaseMosaic" "off"
# Removed Option "metamodes" "GPU-109d4eb8-b40b-87d7-3fd6-95830d1d5215.DVI-I-2: nvidia-auto-select +0+0, GPU-109d4eb8-b40b-87d7-3fd6-95830d1d5215.DVI-I-3: nvidia-auto-select +1280+0, GPU-82e96214-175e-5e6a-218c-5bdbc948daf2.DVI-I-1: nvidia-auto-select +3200+0"
# Removed Option "SLI" "off"
# Removed Option "BaseMosaic" "on"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "nvidiaXineramaInfoOrder" "DFP-0"
    Option         "metamodes" "DVI-I-2: nvidia-auto-select +0+0, DVI-I-3: nvidia-auto-select +1280+0"
    Option         "SLI" "Off"
    Option         "MultiGPU" "Off"
    Option         "BaseMosaic" "off"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Screen"

# Removed Option "metamodes" "nvidia-auto-select +0+0"
# Removed Option "metamodes" "DVI-I-3: nvidia-auto-select +0+0"
    Identifier     "Screen1"
    Device         "Device1"
    Monitor        "Monitor1"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "metamodes" "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" "nvidia-auto-select +0+0"
    Option         "SLI" "Off"
    Option         "MultiGPU" "Off"
    Option         "BaseMosaic" "off"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Here is my old 'working in 12.04' xorg.conf

# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings:  version 310.19  ([email protected])  Thu Nov  8 02:08:55 PST 2012


Section "ServerLayout"

# Removed Option "Xinerama" "0"
    Identifier     "Layout0"
    Screen      0  "Screen0" 0 0
    Screen      1  "Screen1" RightOf "Screen2"
    Screen      2  "Screen2" RightOf "Screen0"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
    Option         "Xinerama" "1"
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      "DELL 1907FP"
    HorizSync       30.0 - 81.0
    VertRefresh     56.0 - 76.0
    Option         "DPMS"
EndSection

Section "Monitor"

    # HorizSync source: unknown, VertRefresh source: unknown
    Identifier     "Monitor1"
    VendorName     "Unknown"
    ModelName      "DELL 1907FP"
    HorizSync       30.0 - 81.0
    VertRefresh     56.0 - 76.0
    Option         "DPMS"
EndSection

Section "Monitor"
    Identifier     "Monitor2"
    VendorName     "Unknown"
    ModelName      "Apple Cinema HD"
    HorizSync       74.0 - 74.6
    VertRefresh     59.9 - 60.0
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GTX 580"
    BusID          "PCI:1:0:0"
    Screen          0
EndSection

Section "Device"
    Identifier     "Device1"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GT 520"
    BusID          "PCI:3:0:0"
EndSection

Section "Device"
    Identifier     "Device2"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GTX 580"
    BusID          "PCI:1:0:0"
    Screen          1
EndSection

Section "Screen"

# Removed Option "metamodes" "DFP-0: nvidia-auto-select +0+0, DFP-2: nvidia-auto-select +1280+0"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "metamodes" "DFP-0: nvidia-auto-select +0+0; DFP-0: nvidia-auto-select +0+0; DFP-0: 1280x1024_75 +0+0; DFP-0: 1152x864 +0+0; DFP-0: 1024x768 +0+0; DFP-0: 1024x768_60 +0+0; DFP-0: 800x600 +0+0; DFP-0: 800x600_60 +0+0; DFP-0: 640x480 +0+0; DFP-0: 640x480_60 +0+0; DFP-0: nvidia-auto-select +0+0 {viewportout=1280x720+0+152}"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen1"
    Device         "Device1"
    Monitor        "Monitor1"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "metamodes" "nvidia-auto-select +0+0"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen2"
    Device         "Device2"
    Monitor        "Monitor2"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "metamodes" "DFP-2: nvidia-auto-select +0+0"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Extensions"
    Option         "Composite" "Disable"
EndSection