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Thread: Ubuntu 12.04 3 monitor setup with 3d support (2 graphics cards, no SLI)

  1. #1
    Join Date
    Sep 2007
    Beans
    10

    Ubuntu 12.04 3 monitor setup with 3d support (2 graphics cards, no SLI)

    Hello everyone,

    I've been looking for about 3 years to find a solution for working with 3 monitors with 3d hardware acceleration in ubuntu. And today I found the best solution, so I'd like to share it with you.

    One possible solution is to disable twinview, run 3 seperate x-servers and combine them with Xinerama. The only problem is that compiz will not work and dragging windows from one screen to another can sometimes be buggy.

    The solution I found was the next:

    1. Remove your old xorg.conf
    2. Check what the addresses are for your monitors (You can check them in the NVIDIA X Server Settings), it should look like GPU-*.DFP-*
    3. Run the following command from a terminal:
      Code:
      sudo nvidia-xconfig --base-mosaic --metamodes="GPU-1.DFP-2: 1680x1050+0+0, GPU-0.DFP-0: 1920x1080+1680+0, GPU-0.DFP-2: 1680x1050+3600+0"
      In here you need to set the correct resolutions and positionings. (I had to start with position +0+0, otherwise it went wrong and my left monitor got cloned to my middle monitor)
    4. If you restart X now, everything will be working, but the screen has lots of lag (3 seconds in my case) which is pretty annoying.


    To fix the lag, you need to set a parameter in Grub2

    1. Edit /etc/default/grub
      Code:
      sudo vi /etc/default/grub
    2. Look for GRUB_CMDLINE_LINUX_DEFAULT=
    3. Add "iommu=pt" to the string after the variable
      It will look like:
      GRUB_CMDLINE_LINUX_DEFAULT="quiet splash iommu=pt"
    4. Now save the file and update your grub
      Code:
      sudo update-grub2
    5. Now all you have to do is restart your machine and everything should be working!


    I hope I can help a lot of people with this solution. Let me know in the comments below if you have any problems.

  2. #2
    Join Date
    Feb 2012
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    24

    Re: Ubuntu 12.04 3 monitor setup with 3d support (2 graphics cards, no SLI)

    Hi i have a post listed already but I am having a problem that I cannot find a solution to anywhere! I have 2 monitors and i am using Xinerama and for some reason I cannot get any 3d effects to work on my desktop. I am using Gnome and for some reason the hotspot in the top left corner doesnt activate. I dont' have any sort of dash whatsoever...just the applications and places tab on top. I'm using an older Nvidia geforce 210 card. When i check my system setting details it says I am in fallback mode. I don't understand why it wont boot into the regular 3d mode. Unity never seemed to have any eye candy either, which makes me thing i was always in 2d and didn't know it.

  3. #3
    Join Date
    Sep 2007
    Beans
    10

    Re: Ubuntu 12.04 3 monitor setup with 3d support (2 graphics cards, no SLI)

    As far as I know Xinerama doesn't support a 3d desktop. You should use Twinview instead to create a multiple monitor desktop with 3d support, or try the solution above if you have multiple graphics cards.

  4. #4
    Join Date
    Jun 2012
    Beans
    1

    Re: Ubuntu 12.04 3 monitor setup with 3d support (2 graphics cards, no SLI)

    Arjenzwerver, I have also spent an obscene amount of time looking for a solution to the dualhead three monitor linux setup and have spent the last year with a half-baked setup involving two x-screens with twinview. I had almost given up until I ran into your post. I cannot thank you enough; you have made my week.

  5. #5
    Join Date
    Sep 2007
    Beans
    10

    Talking Re: Ubuntu 12.04 3 monitor setup with 3d support (2 graphics cards, no SLI)

    I'm glad tot hear that it helped!

  6. #6
    Join Date
    Aug 2011
    Beans
    4
    Distro
    Xubuntu 11.04 Natty Narwhal

    Re: Ubuntu 12.04 3 monitor setup with 3d support (2 graphics cards, no SLI)

    Can I ask what card you're using?

    I seem to have misread the documentation for BaseMosaic and thought it was a more general version of SLI Mosaic for nvidia cards, but it seems it's just Quadros and related cards.

  7. #7
    Join Date
    Sep 2007
    Beans
    10

    Re: Ubuntu 12.04 3 monitor setup with 3d support (2 graphics cards, no SLI)

    I'm using 2x Nvidia GTX 560 Ti. SLI is not enabled in this configuration.

    For SLI mosaic you need an NVIDIA Quadro graphics card which I don't have.

  8. #8
    Join Date
    Aug 2011
    Beans
    1

    Re: Ubuntu 12.04 3 monitor setup with 3d support (2 graphics cards, no SLI)

    Fantastic. I have 3head setups at work and at home, and this fixed them right up for me. Now I can use Gnome3, which I prefer to Unity.

    Thank you!

  9. #9
    Join Date
    Mar 2010
    Beans
    1

    Re: Ubuntu 12.04 3 monitor setup with 3d support (2 graphics cards, no SLI)

    Thank you for posting this! Works great!!!

    3 monitor setup with full acceleration - Kubuntu 12.04 and 2 gtx 550ti's.

  10. #10
    Join Date
    Sep 2012
    Beans
    1

    Re: Ubuntu 12.04 3 monitor setup with 3d support (2 graphics cards, no SLI)

    The iommu=pt option didn't help with me, as the iommu on my intel x58 board (shuttle sx58h7) isn't used.

    Enabling it with intel_iommu=on leads to x locking up and vt switching not working when the nvidia module is loaded.

    I'm not sure if this is the bios at fault (it seems to be doing something dodgy with the onboard audio and the iommu, although the workaround looks like it only affects the onboard audio) or the nvidia module, but either way enabling the iommu doesn't seem to be an option.

    Also the 'lag' here was more like 20-30 seconds (gtx 295).

    I figured out quite quickly that disabling composite at least got me a setup where xrandr knows what's going on with the 3 monitors (unlike xinerama, or using a triplehead2go).

    I then eventually worked out that using xrender instead of opengl for compositing also works round the painful lag (in kubuntu at least). Some effects aren't available, but it looks a whole lot better than without.

    Thanks for pointing me in the right direction with the basemosaic option!

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