Multiseat or multihead for multiple desktops?

Support Graphics & Display
1

I have a MAG X670E with a 9800x3d and a 7900 xt.
I want to run multiple desktops one as a normal desktop and one as a kodi mediacenter and some game launcher.
I need to use one HDMI port from the GPU and one from the motherboard as I need two 4K 120hz outputs using HDMI.
Also all desktops need to use the big GPU for hardware acceleration, I can’t run games or demanding emulators on the iGPU.
Audio should go through HDMI, needs a 10-band equalizer similar to windows with realtek drivers.
The individual desktops should run independently from each other, I don’t want windows moving from one to the other or any kind of focus stealing problems.

What’s the best way to do this?
What about input devices? Keyboard, mouse, Bluetooth/USB gamepads?

2

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3

Last time I installed Kodi, it was automatically positioned as a separate session (at least, on KDE); in which case it’s selected from the SDDM login screen (bottom/left). I mention this only in case you are yet to install Kodi.

In some other distributions it simply installs as a normal application.

As mentioned (above) some system information would be helpful.

Regards.

4

This will be a real multiseat setup

Since this is seldom used, you may stumble into problems from time to time. :man_shrugging:

I do use a multiseat system with xfce4 and 2 separate seats. So i will give you some hints. But (!) this cant be a step by step, because my usage differs from what you want.

  • You may need to use 2 different graphic cards for these seats
  • You may need 2 different mice and keyboards
  • I do not use any xorg or nvidia configfiles (because they tend to break with every next update)
  • I had to change my
/etc/lightdm/lightdm.conf 
lightdm cat lightdm.conf| grep -Ev '^#'
[LightDM]
logind-check-graphical=false
run-directory=/run/lightdm
[Seat:*]
greeter-session=lightdm-gtk-greeter
greeter-hide-users=false # Bug: lightdm-gtk-greeter does not load user saved session when greeter-hide-users=true[1]
session-wrapper=/etc/lightdm/Xsession
[Seat:seat0]
xserver-command=/usr/bin/X :0 -isolateDevice PCI:39:0:0 vt8
xserver-layout=seat0
[Seat:seat1]
xserver-command=/usr/bin/X :1 -isolateDevice PCI:1:0:0 -novtswitch vt6
xserver-layout=seat1
[XDMCPServer]
[VNCServer]
  • i do use sudo loginctl to manage the seats (Do not get confused by the names of the seats.)
sudo loginctl list-seats
SEAT 
seat0
seat1

2 seats listed.
  • I did use an separate USB-Hub dedicated for devices attached to seat1 (mouse, keyb, usb-sticks …)
  • At the beginning each and every device belongs to seat0
  • Examples
sudo loginctl attach seat1 /sys/devices/pci0000:00/0000:00:01.1/0000:01:00.0/graphics/fb1
sudo loginctl attach seat1 /sys/devices/pci0000:00/0000:00:07.1/0000:28:00.3/usb3/3-2/3-2.3  
sudo loginctl attach seat1 /sys/devices/pci0000:00/0000:00:03.1/0000:27:00.1/sound/card1 
...
sudo loginctl attach seat1 /sys/devices/pci0000:00/0000:00:01.3/0000:03:00.0/usb1/1-7/1-7.3/1-7.3:1.1/0003:062A:4101.0012/input/input60
...
sudo loginctl attach seat1 /sys/devices/pci0000:00/0000:00:01.3/0000:03:00.0/usb1/1-7/1-7.3/1-7.3:1.1/0003:062A:4101.0012/input/input63

I wish you much success (you may need it) :footprints:

5

4k@120 Hz with an amd-gpu via hdmi is not possible due to the reason that the hdmi-foundation rejected and forbid that amd implement it to a open source-driver. 4k@120Hz with amd is provided with dp-ports but not with hdmi.

6

@andreas85
If I need a dedicated GPU per seat then this won’t work for me. I need to be able to use the outputs from any GPU in the system but use the fast GPU for any rendering/acceleration.
I thought having multiple independent sessions would we quiet nice to have, then I would just need to switch to another input on my TV and can easily switch between things, but If I need multiple big GPUs I might as well just repurpose my current desktop.

@Olli
What seriously? I’m currently still running windows 10 on my desktop and having 4K@120hz with HDMI just works, I need HDMI as I am using LG OLED TVs as screens and they don’t have any display ports.
I was trying DP to HDMI adapters on windows but couldn’t get 4k@120hz working with it, so I have another weaker GPU in my windows desktop and use 1 HDMI on each card which works just fine.
Can I get 4k@120hz running on Linux over DP, with an adapter, with my LG OLED TVs?

Would an nvidia 4000 series card work?

7

You can not switch a seat(monitor) from one GPU to another (as you would need to unplug the cable and replug it into the other GPU :laughing: )

I think you are seriously underestimating how little GPU power is really required for individual tasks. (Games may require a relatively high level of power, but using a browser or a video was already possible with graphics cards from 30 years ago.)

This already are 2 separate graphic cards !

:footprints:
I recommend that you set up the basic system and then move towards your goal step by step. There is no complete plan with a guarantee of success when your expectations are so high.

8

Should be possible

 $ inxi -Gxxx
Graphics:
  Device-1: Advanced Micro Devices [AMD/ATI] Navi 31 [Radeon RX
    7900 XT/7900 XTX/7900 GRE/7900M] vendor: Tul / PowerColor
    driver: amdgpu v: kernel arch: RDNA-3 pcie: speed: 16 GT/s
    lanes: 16 ports: active: DP-2 empty: DP-1, DP-3, HDMI-A-1,
    Writeback-1 bus-ID: 63:00.0 chip-ID: 1002:744c class-ID: 0300
  Display: wayland server: X.org v: 1.21.1.15 with: Xwayland
    v: 24.1.5 compositor: kwin_wayland driver: X: loaded: modesetting
    alternate: fbdev,vesa dri: radeonsi gpu: amdgpu display-ID: 0
  Monitor-1: DP-2 model: Samsung LS49AG95 serial: HNTR900132 res:
    mode: 5120x1440 hz: 240 scale: 100% (1) dpi: 82
    size: 1193x336mm (46.97x13.23") diag: 1239mm (48.8") modes:
    max: 5120x1440 min: 720x400
  API: EGL v: 1.5 hw: drv: amd radeonsi platforms: device: 0
    drv: radeonsi device: 1 drv: swrast gbm: drv: kms_swrast
    surfaceless: drv: radeonsi wayland: drv: radeonsi x11:
    drv: radeonsi
  API: OpenGL v: 4.6 compat-v: 4.5 vendor: amd mesa
    v: 24.3.4-arch1.1 glx-v: 1.4 direct-render: yes renderer: AMD
    Radeon RX 7900 XTX (radeonsi navi31 LLVM 19.1.7 DRM 3.60
    6.14.0-rc1-next-20250204-1-next-git-01375-g40b8e93e17bf-dirty)
    device-ID: 1002:744c display-ID: :0.0
  API: Vulkan v: 1.4.303 layers: 9 surfaces: xcb,xlib,wayland
    device: 0 type: discrete-gpu driver: N/A device-ID: 1002:744c
    device: 1 type: discrete-gpu driver: N/A device-ID: 1002:744c
  Info: Tools: api: clinfo, eglinfo, glxinfo, vulkaninfo
    de: kscreen-console,kscreen-doctor gpu: corectrl wl: wayland-info
    x11: xdpyinfo, xprop, xrandr
9

cause the windows-driver is propietary, non-free but the amd-driver for linux is open-source and the hdmi-foundation rejects to make driver-code public as described in the article.

trial-and-error… it depends on the display-firmware the cables and the adapter. it might it might not work.

to get troubled with the typical nvidia-bull$hit-problems ? you need these displays just for a mediacenter, in this case have a look at the actual intel-cards (b580) but you have to get information about them. a pro for the intel-card is that the video-codecs are implemented as hardware while they are implemented as software by nvidia. saw a video-tutorial about this problem in the past. 2 video-cams running 24/7 for a security-entrance. the power-consumption was 35 watts while encoding them with nvidia and dropped to 7-15 watts when changed to intel. the hardware-integration of the codecs is a pretty nice advantage in such cases.

10

With careful research you might find a KVM Switch that would allow you to manually swap graphic outputs between two monitors; not a typical configuration, but still possible with the right KVM.

Good luck.