How can I run 3 monitors (2 video cards) on Linux Mint 15?

Question

I am trying to switch my PC from Windows to Linux Mint 15. I have three monitors that work very well in Windows. After installing Mint (and seeing that it naturally only uses 1 monitor) I tried to use "Displays" to add the other two; however, doing this does not utilize my two Nvidia GeForce 9600 video cards. The screens flashes repeatedly and the entire system slows down. I have installed nvidia drivers using sudo apt-get install nvidia-current and by downloading and running the "NVidia...run" files provided by Nvidia. Then, using the nvidia Server x config, enabled the other two monitors. Whenever I do this and restart the x service, all three monitors are enabled but Cinnamon crashes repeatedly (leaving a strange, unusable desktop where all tray icons and menus are triplicated on the primary monitor).

How can I get all 3 monitors to work (One desktop spanning three monitors)?

I have tried searching all over and while this is discussed many times in many places, none of these discussions are both up to date and comprehensive (and the few that are close lead to the above results).

I will add any information necessary to the question.

Info:

Returned from inxi -Gx:

Graphics:  Card-1: NVIDIA G94 [GeForce 9600 GT] bus-ID: 01:00.0 
           Card-2: NVIDIA G94 [GeForce 9600 GT] bus-ID: 02:00.0 
           X.Org: 1.13.3 driver: nvidia Resolution: 4320x900 
           GLX Renderer: GeForce 9600 GT/PCIe/SSE2 GLX Version: 3.3.0 NVIDIA 304.88 Direct Rendering: Yes

Returned from cinnamon --version:
Cinnamon 1.8.8

This is a working Nvidia generated xorg.conf for a single screen:

# nvidia-xconfig: X configuration file generated by nvidia-xconfig
# nvidia-xconfig:  version 304.88  (buildmeister@swio-display-x86-rhel47-06)  Wed Mar 27 15:32:58 PDT 2013

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
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"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Unknown"
    HorizSync       28.0 - 33.0
    VertRefresh     43.0 - 72.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

This is not a working Nvidia generated xorg.conf:

# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings:  version 304.88  (buildd@lamiak)  Wed Apr 10 16:20:15 UTC 2013

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0" 0 0
    Screen      1  "Screen1" 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      "HannStar Display Corp Hanns.G HW191"
    HorizSync       30.0 - 83.0
    VertRefresh     49.0 - 75.0
    Option         "DPMS"
EndSection

Section "Monitor"
    # HorizSync source: unknown, VertRefresh source: unknown
    Identifier     "Monitor1"
    VendorName     "Unknown"
    ModelName      "HannStar Display Corp Hanns.G HW191"
    HorizSync       0.0 - 0.0
    VertRefresh     0.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce 9600 GT"
    BusID          "PCI:1:0:0"
EndSection

Section "Device"
    Identifier     "Device1"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce 9600 GT"
    BusID          "PCI:2:0:0"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "nvidiaXineramaInfoOrder" "CRT-0"
    Option         "metamodes" "nvidia-auto-select +0+0"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen1"
    Device         "Device1"
    Monitor        "Monitor1"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "metamodes" "CRT-0: nvidia-auto-select +0+0, CRT-1: nvidia-auto-select +1440+0"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

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

Solution

I tried for several weeks to get this to work on my machine (HP XW8400 with 2 identical NVS 290 cards) to no avail. Ended up switching to KDE and everything worked just fine. I'm sure that's not what you wanted to hear, but give this a go:

In the NVIDIA tool, you need to enable all 3 monitors. You can just enable them with a separate X Screen for now with Xinerama checked. This won’t actually get what you want, but it’ll allow the command below to work.

sudo nvidia-xconfig --separate-x-screens --render-accel --xinerama

If you get errors, ensure that there are double dashes infront of the three command options. The output should look like this:

user@host:~$ sudo nvidia-xconfig --separate-x-screens --render-accel --xinerama

Using X configuration file: "/etc/X11/xorg.conf".
Option "RenderAccel" "True" added to Screen "Screen0".
Option "RenderAccel" "True" added to Screen "Screen1".
Option "RenderAccel" "True" added to Screen "Screen2".

WARNING: The Composite X extension does not currently interact well with the
         Xinerama option; the Composite X extension will be disabled.

Backed up file '/etc/X11/xorg.conf' as '/etc/X11/xorg.conf.backup'
New X configuration file written to '/etc/X11/xorg.conf'

Again, I wasn't able to get this to work on Cinnamon (i.e. booted into "Failback Mode"). Give it a shot and let's see what happens.

Comments

[terdon]

Which version of Cinnamon are you using (cinnamon --version)? Cinnamon is still new and under active development, I had trouble with my 2 screens not too long ago which was fixed when I upgraded to Cinnamon 1.8.2.

[roundar]

Running cinnamon 1.8.8. Question updated.

[terdon]

Hmm, not that then. Could you post the /etc/X11/xorg.conf file generated by nvidia-settings and also explain what your desired setup is. Do you want one desktop spanning the 3 screens or mirrored desktops or separate desktops on each screen etc.

[roundar]

Added two: A working Nvidia generated xorg.conf and a non-working xorg.conf. I am trying to have one desktop spanning 3 screens.

[terdon]

What do you mean working? If it is working use it. I assume it is not working the way you want?

[roundar]

Working as in one monitor without crashing. When the other monitors are added, cinnamon crashes (after reboot). Note the working xorg.conf only has 1 screen and monitor listed.