Triple Monitor Setup Issues with RTX 4070 Ti - Inconsistent Behavior and Mirroring Problems

User Support Hardware Issues
1

TL;DR

Three 1920x1080 monitors (1 HDMI, 2 DisplayPort) connected to RTX 4070ti have inconsistent behavior in Qubes OS 4.2.3 - monitors randomly fail to turn on, unwanted mirroring occurs, and display configuration tools (lxrandr) are unresponsive or limited. Same setup works perfectly in NixOS.

System Specifications

  • OS: Qubes OS 4.2.3
  • CPU: AMD Ryzen 7 3700X @ 4.43 GHz
  • RAM: 32GB DDR4
  • GPU: NVIDIA RTX 4070ti

Hardware Setup

  • Monitors: 3x 1920x1080
    • Monitor 1 (Left): HDMI connection, capable of 75Hz
    • Monitor 2 (Middle, Main): DisplayPort connection, capable of 244Hz
    • Monitor 3 (Right): DisplayPort connection
  • Total Resolution: 5760x1080
  • Note: This exact setup works correctly on NixOS
  • Future Goal: Configure different refresh rates (244Hz for main monitor, 75Hz for left monitor) once basic functionality is established

Symptoms

  1. Inconsistent Monitor Detection

    • Sometimes only 2/3 monitors activate
    • Main DisplayPort monitor always works
    • Other monitors randomly work/don’t work

  2. Display Configuration Issues

    • Random mirroring of right monitor (DisplayPort) with no way to change
    • Left monitor (HDMI) sometimes completely off
    • Issues persist in both XFCE and i3

  3. Incorrect Monitor Layout When “Working”

    • From middle monitor (main DisplayPort):
      • Moving mouse right does nothing
      • Moving mouse left goes to right monitor (secondary DisplayPort)
      • Moving mouse left again goes to left monitor (HDMI)
    • Layout is completely different from physical monitor arrangement
    • Unable to correct this through normal means

  4. LXRandr Problems

    • Usually only detects 2 monitors
    • When 3 monitors detected, forces mirroring mode
    • Often freezes and reverts changes
    • Cannot modify display arrangement

Attempted Solutions

  1. Tried multiple configuration methods:

    • XFCE Display Settings: Limited detection and configuration issues (detailed above)
    • i3 config with xrandr commands: No effect
    • LXRandr: Limited detection and configuration issues (detailed above)

  2. Modified GUI video RAM settings:

qvm-features dom0 gui-videoram-min $(($WIDTH * $HEIGHT * 4 / 1024))
qvm-features dom0 gui-videoram-overhead 0
  • Calculated for 5760x1080 (~22 MiB)
  1. Tried automatic video RAM calculation:
qvm-features dom0 gui-videoram-min $(xrandr --verbose | grep "Screen 0" | sed -e 's/.*current //' -e 's/\,.*//' | awk '{print $1*$3*4/1024}')

  1. Tested different kernels (using latest from installer)

  2. Attempted NVIDIA proprietary driver installation following this guide

    • yumdownloader --resolve xorg-x11-drv-nvidia failed
    • Guide unclear on next steps

Questions

  1. Is triple monitor setup supported in Qubes OS?
  2. Are there known issues when using Qubes OS with the NVIDIA RTX 4070ti?
  3. Should I pursue the proprietary driver installation, and if so, what are the correct steps?
  4. Given that this setup works perfectly in NixOS, what might be the Qubes-specific issues I should investigate?
1 Like
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  1. In general, yes. I’m typing this out on a triple monitor system.

  2. ?

  3. On performance and usability grounds, I would recommend Nvidia’s open-source driver over nouveau. Others may be able to comment on the security implications of this choice, if any. In my case, I installed the Nvidia driver obtained directly from Nvidia’s site, where you can search for the correct driver for your card. Supplying the installer “-m kernel-open” will select the open-source driver during the build process. Make sure to blacklist nouveau.

  4. This really sounds like an X11 issue, and I’m guessing you’re running Wayland on NixOS. You can debug X issues by looking through /var/log/Xorg.0.log and searching for GPU-related issues in dmesg. In my case, I needed to hand code /etc/X11/xorg.conf and pass the kernel “nvidia-drm.modeset=1” to obtain the desired result.

2 Likes
3

Thank you for the reply.

I did what you said and installed the Nvidia driver from their website, moved it to dom0, ran it with the open-source flag, finished installation, and then modified my xorg.conf like you did. This fixed my three monitors not working.

Just to add on, for some reason when I set my monitor configuration in my i3 config with xrandr it doesn’t persist, do you know why that is? Any other change I make to my i3 configurations seems to persist but not the monitor changes.

1 Like
4

Changes made with xrandr will only persist for the current session (this is normal). For a more a more durable solution, you’ll need to update your xorg configuration file.

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