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Thread: AMD RX5700 Dual Monitors, One Using an Incorrect Lower Resolurion

  1. #1
    Join Date
    Aug 2013
    Beans
    17

    AMD RX5700 Dual Monitors, One Using an Incorrect Lower Resolurion

    I have a new setup with an AMD graphics card. I attach two 1920x1080 monitors, one via DVI and the other by HDMI. The latter does not have it’s native resolution of 1920x1080, but a lower one of 1024x768 (it used to be much lower at 858x480 when I first booted into Ubuntu).

    In Ubuntu Settings→Devices→Screen Display the wayward monitor is identified as “Unknown Display”. The other is correctly identified.

    I have a new install of Ubuntu 19.10, completely updated. I have not installed any additional graphics drivers. It is using AMDGPU, which is (I think) what it should be using.

    Details of setup:

    mainboard: ASUS Prime x570-Pro
    CPU: AMD Ryzen 5 3600X
    GPU MSI Armor RX570 (1xDVI, 1xHDMI, 3xDP)
    Memory: 32GB DDR4
    Power Supply: 600W

    Neither of my monitors support DP.

    Using another computer and connecting the wayward monitor via HDMI (same cable), it uses and reports the correct native resolution.

    Using a DP to HDMI cable from the RX5700 to the wayward monitor gives the same lower resolution.

    I read that AMD only support LTS versions of Ubuntu, so I tried 18.04 via a Live USB. Same results.

    If I connect the wayward monitor on its own via DVI it displays the correct resolution. (Unfortunately, I cannot just swap the cables and monitors as one monitor only supports DVI and the <wayward> one has DVI and HDMI.)

    Some information from terminal commands:

    xrandr reports:
    xxxxx:~$ xrandr
    Screen 0: minimum 320 x 200, current 2944 x 1080, maximum 16384 x 16384
    DisplayPort-0 disconnected (normal left inverted right x axis y axis)
    DisplayPort-1 disconnected (normal left inverted right x axis y axis)
    DisplayPort-2 disconnected (normal left inverted right x axis y axis)
    HDMI-A-0 connected 1024x768+1920+0 (normal left inverted right x axis y axis) 0mm x 0mm
    1024x768 60.00*
    800x600 60.32 56.25
    848x480 60.00
    640x480 59.94
    DVI-D-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 477mm x 268mm
    1920x1080 60.00*+
    1600x1200 60.00
    1680x1050 59.88
    1280x1024 75.02 60.02
    1440x900 59.90
    1280x960 60.00
    1152x864 75.00
    1024x768 75.03 70.07 60.00
    832x624 74.55
    800x600 72.19 75.00 60.32 56.25
    640x480 75.00 72.81 66.67 59.94
    720x400 70.08

    ---------------------------------------------------------------------

    xxxxx:~$ sudo lspci -nnk | grep -i vga -A3 | grep 'in use'
    [sudo] password for xxxx:
    Kernel driver in use: amdgpu

    ---------------------------------------------------------------------

    xxxxx:~$ sudo lshw -c video
    *-display
    description: VGA compatible controller
    product: Ellesmere [Radeon RX 470/480/570/570X/580/580X/590]
    vendor: Advanced Micro Devices, Inc. [AMD/ATI]
    physical id: 0
    bus info: pci@0000:07:00.0
    version: ef
    width: 64 bits
    clock: 33MHz
    capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
    configuration: driver=amdgpu latency=0
    resources: irq:85 memory:e0000000-efffffff memory:f0000000-f01fffff ioport:e000(size=256) memory:fcf00000-fcf3ffff memory:fcf40000-fcf5ffff

    ---------------------------------------------------------------------

    I also tried adding amdgpu.dc=0 to the kernel parameters to no effect.

    I have been working on this for two days. I cannot find out if the MSI Armor RX5700 does or does not support DVI and HDMI working together. And obviously, I have not been able to resolve the situation myself.

    Any ideas?

    Thanks in advance.

    -- Zoot

  2. #2
    Join Date
    Jun 2007
    Beans
    14,248

    Re: AMD RX5700 Dual Monitors, One Using an Incorrect Lower Resolurion

    Could we see a /var/log/Xorg.0.log ?

  3. #3
    Join Date
    Aug 2013
    Beans
    17

    Re: AMD RX5700 Dual Monitors, One Using an Incorrect Lower Resolurion

    Quote Originally Posted by Yellow Pasque View Post
    Could we see a /var/log/Xorg.0.log ?
    I have looked in /var/log and I do not have an Xorg.0.log. I only have the following log files in that directory:

    /var/log$ ls *.log
    alternatives.log boot.log fontconfig.log ubuntu-advantage.log
    apport.log bootstrap.log gpu-manager.log
    auth.log dpkg.log kern.log


    In case it may be relevant, I checked my Ubuntu login screen and I log into my username using Ubuntu not Ubuntu with Wayland.

    -- Zoot

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