6 Monitor Config with dual Nvidia GPUs

Hi Folks!

I jumped ship from windows 10 recently and have installed KDE Neon after trying out Mint, Solar and a couple other distros. I’ve got a little bit of linux knowledge but not very hot on the X11 side of things. Hopefully someone can point me in the right direction on this - there’s lots online about setting up dual or triple monitors but not much that’s helpful to me

I’ve got 6 monitors (4 x 4k and 2 x 1440p) and 2 Nvidia cards (1070 and 980, man they suck in Linux lol). I’ve rearranged the monitors in Nvidia X Server Settings so that they are in a 2x2 grid instead of next to each other in a row (The 6 monitor config i’d like is 3 x 2 (3 monitors horizotally by 2 vertically)). The 4 monitor that are enabled appear to be all running off of ‘X Screen 0’ which running on the 1070.

So the 2 screens physically connected to the 980 are not used. I’ve tried turning on the 2 extra monitors and in Nvidia X Config they are both disabled. There is a dropdown list with the option to create ‘New X Screen (requires X restart)’. I’ve tried this and it tries to create X Screen 1 but when I hit apply it gives the following error (my comments in parenthesis):


  • Location of an X screen has changed (not moved anything)
  • location or type of an x screen has changed (possibly the new screen? not sure)
  • the color depth of an x screen has changed (possibly the new screen? not sure)
  • an x screen has been added or removed (the new screen!)
  • xinerama is being enabled/disabled (xinerama is disabled)

For all the requested settings to take effect, you must save the configuration to the x config file and restart the x server. (i’ve not created an x config file yet)

This is what the ‘Save to X Configuration File’ button in the Nvidia X Server Settings application churns out if I run it and hit preview (Doesn’t look like it’s got all the monitors in there to me?):

###########################

nvidia-settings: X configuration file generated by nvidia-settings

nvidia-settings: version 390.77 (buildd@lcy01-amd64-022) Thu Sep 6 07:51:39 UTC 2018

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 “BenQ 241W”
HorizSync 30.0 - 83.0
VertRefresh 56.0 - 76.0
Option “DPMS”
EndSection

Section “Device”
Identifier “Device0”
Driver “nvidia”
VendorName “NVIDIA Corporation”
BoardName “GeForce GTX 1070”
BusID “PCI:65:0:0”
EndSection

Section “Screen”
Identifier “Screen0”
Device “Device0”
Monitor “Monitor0”
DefaultDepth 24
Option “Stereo” “0”
Option “nvidiaXineramaInfoOrder” “DFP-6”
Option “metamodes” “DVI-D-0: nvidia-auto-select +640+960, DP-0: nvidia-auto-select +2560+0, DP-2: 2560x1440_144 +0+2160, DP-4: nvidia-auto-select +2560+2160”
Option “SLI” “Off”
Option “MultiGPU” “Off”
Option “BaseMosaic” “off”
SubSection “Display”
Depth 24
EndSubSection
EndSection

###########################

I’m not sure where this needs to be saved in KDE Neon so I’ve not tinkered with it or tried to edit it yet

Any help appreciated - happy to check documents but scared I’ll end up down a rabbit hole if i’m on the wrong path and break something!

Thanks
Sunny

That won’t work in a satisfactory way, at least not with two Geforce-type cards. This would limit you to using Xinerama and you won’t want that.
If you also have a integrated intel gpu, remove the 980, enable and use the outputs of the igpu and the 1070 in a PRIME setup. IIRC, KDE Neon uses Ubuntu as base system, this will set this up automatically by installing the package nvidia-prime and running
sudo prime-select nvidia

Thanks for the help Generix. Unfortunately I don’t have an onboard GPU as I’m running a Ryzen board. Ironically do you know if that setup would work if I bought an AMD GPU, swapped it out for the 980 and did the same thing?

Or do you know of any other solutions?

Thanks
Sunny

Swapping in a low-end AMD graphics card and use its outputs in a PRIME setup should work, in theory. In practice, I can’t promise because I actually don’t know, lacking experience in that case.
You can still try a Xinerama setup, you can use nvidia-xconfig to create an xorg.conf for you:
sudo nvidia-xconfig -o /etc/X11/xorg.conf --xinerama
but that setup has a lot of downsides, you’ll notice.
Then, there’s the rabbit hole, trying to get two nvidia cards working using PRIME:
https://devtalk.nvidia.com/default/topic/1046154/linux/split-kernel-driver-working-now-i-need-to-configure-the-monitors-on-second-gpu-i-m-lost-/
But that’s kind of advanced chemistry and was not working correctly the last time.

Thanks Generix! I’ll take a look into these options