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Thread: Issue with Second Display Monitor (Unknown Display) and Missing 1600x900 Resolution

  1. #1
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    Issue with Second Display Monitor (Unknown Display) and Missing 1600x900 Resolution

    Hello Ubuntu Community,


    I am facing an issue with my second display monitor on Ubuntu, and I'm seeking assistance to resolve it. Here are the details of my problem:


    1. Hardware Configuration:
    - Graphics Card: AMD/ATI Caicos [Radeon HD 6450/7450/8450 / R5 230 OEM]
    - Monitor: Connected via VGA, supports 1600x900 resolution


    2. Problem Description:
    - The second display monitor is recognized as "Unknown Display" in Ubuntu.
    - The available resolutions for the second display are limited to 1024x768, 848x480, and 800x600.
    - The desired resolution of 1600x900 is not available for the second display.


    3. Dual Boot Setup:
    - I have a dual boot configuration with Windows 7 and Ubuntu.
    - In Windows 7, the second display monitor works fine and supports the 1600x900 resolution without any issues.


    I have already tried the following steps to resolve the issue, based on suggestions received earlier:


    - Installed the "xserver-xorg-video-radeon" package.
    - Used the "xrandr" command to add a new mode for 1600x900 resolution.
    - Checked for additional drivers using the "Additional Drivers" tool, but no suitable driver was found.


    Despite these efforts, the issue persists, and I'm unable to set the desired resolution for my second display monitor on Ubuntu.


    I kindly request the Ubuntu community's assistance in resolving this issue. If you have any suggestions, insights, or possible solutions, I would greatly appreciate your guidance.


    Thank you in advance for your help!

  2. #2
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    Re: Issue with Second Display Monitor (Unknown Display) and Missing 1600x900 Resoluti

    Please run the UbuntuForums 'system-info' script and Post the URL of the pastebin the report uploads to.

    It has an extensive Graphics section that will tell us your hardware, settings and what it see's from Linux. We will then review it and come up with recommendations for a solution.

    "Concurrent coexistence of Windows, Linux and UNIX..." || Ubuntu user # 33563, Linux user # 533637
    Sticky: Graphics Resolution | UbuntuForums 'system-info' Script | Posting Guidelines | Code Tags

  3. #3
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    Re: Issue with Second Display Monitor (Unknown Display) and Missing 1600x900 Resoluti


  4. #4
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    Re: Issue with Second Display Monitor (Unknown Display) and Missing 1600x900 Resoluti

    At the Graphical Login screen, after you select the user, use the gear icon on the lower right to select Xorg, instead of Wayland... Does the resolution work then?

    "Concurrent coexistence of Windows, Linux and UNIX..." || Ubuntu user # 33563, Linux user # 533637
    Sticky: Graphics Resolution | UbuntuForums 'system-info' Script | Posting Guidelines | Code Tags

  5. #5
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    Re: Issue with Second Display Monitor (Unknown Display) and Missing 1600x900 Resoluti

    You might want to try to read the EDID (extended display ID). The package read-edid contains get-edid and parse-edid which you call like this:
    Code:
    sudo get-edid|parse-edid
    This should give you all the information both of your displays give your PC about themselves. If your second display isn't shown in the output then either the VGA cable doesn't have all pins connected - specifically it would be missing three pins for the Display Data Channel - or the VGA connector on your graphics card doesn't implement DDC.

    Holger

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    Re: Issue with Second Display Monitor (Unknown Display) and Missing 1600x900 Resoluti

    I'm thinking it is having a problem reading the EDID with Wayland, which is sometimes a problem with Wayland.

    After changing to Xorg, rerun
    Code:
    xrandr -q
    FYI -- 'get-edit' and 'parse-edid' commands are part of package 'read-edid' which would have to be installed. Not a default installed package...
    Last edited by MAFoElffen; May 12th, 2023 at 06:12 PM.

    "Concurrent coexistence of Windows, Linux and UNIX..." || Ubuntu user # 33563, Linux user # 533637
    Sticky: Graphics Resolution | UbuntuForums 'system-info' Script | Posting Guidelines | Code Tags

  7. #7
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    Re: Issue with Second Display Monitor (Unknown Display) and Missing 1600x900 Resoluti

    I tried your suggestion, still the resolution doesn't change, I mean the problem of the unknown display and the resolution 1600x900 is missing.

  8. #8
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    Re: Issue with Second Display Monitor (Unknown Display) and Missing 1600x900 Resoluti

    this is the output:
    This is read-edid version 3.0.2. Prepare for some fun.
    Attempting to use i2c interface
    Problem requesting slave address: Device or resource busy
    No EDID on bus 1
    No EDID on bus 3
    No EDID on bus 4
    No EDID on bus 5
    No EDID on bus 6
    No EDID on bus 7
    No EDID on bus 8
    No EDID on bus 9
    No EDID on bus 10
    No EDID on bus 11
    No EDID on bus 12
    No EDID on bus 13
    No EDID on bus 14
    1 potential busses found: 2
    256-byte EDID successfully retrieved from i2c bus 2
    Looks like i2c was successful. Have a good day.
    Checksum Correct


    Section "Monitor"
    Identifier "SA240Y"
    ModelName "SA240Y"
    VendorName "ACR"
    # Monitor Manufactured week 18 of 2021
    # EDID version 1.3
    # Analog Display
    DisplaySize 530 300
    Gamma 2.20
    Option "DPMS" "true"
    Horizsync 31-75
    VertRefresh 56-75
    # Maximum pixel clock is 180MHz
    #Not giving standard mode: 1152x864, 75Hz
    #Not giving standard mode: 1280x1024, 60Hz
    #Not giving standard mode: 1280x720, 60Hz
    #Not giving standard mode: 1280x800, 60Hz
    #Not giving standard mode: 1440x900, 60Hz
    #Not giving standard mode: 1680x1050, 60Hz
    #Not giving standard mode: 1920x1080, 60Hz
    Modeline "Mode 0" 148.50 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync
    EndSection

    The acer monitor is reflected, but my lg monitor is not shown here.

  9. #9
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    Re: Issue with Second Display Monitor (Unknown Display) and Missing 1600x900 Resoluti

    Is the LG also not seen by xrandr? And which display is connected to the DVI and HDMI?

    "Concurrent coexistence of Windows, Linux and UNIX..." || Ubuntu user # 33563, Linux user # 533637
    Sticky: Graphics Resolution | UbuntuForums 'system-info' Script | Posting Guidelines | Code Tags

  10. #10
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    Re: Issue with Second Display Monitor (Unknown Display) and Missing 1600x900 Resoluti

    If not seen by
    Code:
    xrandr -q --verbose
    But is seen by
    Code:
    xrandr --listmonitors
    Then I think I know what is going on...

    I asked the questions about what display is connected to what port on that Radeon card in my last post (unanswered)... That Radeon card has 3 ports= HDMI, DVI, and VGA. I am assuming that the primary display is connected to the HDMI and the secondary display is connected to the DVI port, through a DVI to HDMI cable or adapter of the same...
    Display Data Channel (DDC)
    Main article: Display Data Channel

    The Display Data Channel (DDC) is a communication channel based on the I2C bus specification. HDMI specifically requires the device implement the Enhanced Display Data Channel (E-DDC), which is used by the HDMI source device to read the E-EDID data from the HDMI sink device to learn what audio/video formats it can take.[5]: §§8.1,CEC-1.2–CEC-1.3  HDMI requires that the E-DDC implement I2C standard mode speed (100 kbit/s) and allows it to optionally implement fast mode speed (400 kbit/s).[5]: §4.2.8 

    The DDC channel is actively used for High-bandwidth Digital Content Protection (HDCP).
    DVI ports are missing those two channels, (in the conversion from HDMI), so the card cannot get the EDID of the display.

    Two ways around that...

    Option #1: One way is to use xrandr to define and add the new mode to the port. This is not persistent. So would have to be added to ~/.xinitrc file to add the mode after User login... Or define and add from an xorg.conf file.

    This link explains how to add a new mode, via those two different methods: https://ubuntuforums.org/showthread....8#post10907238

    Option #2: Use 'get-edid' to extract the EDID to a raw file saved somewhere on the system, so you can include it in an xorg.conf file. You can do this by temporarily connecting the display via the HDMI port, to extract the EDID... That way the system sees "all" the modes the LG display can do natively. Better, cleaner solution.

    The following two links should explain how to do that--
    RE:
    https://manpages.ubuntu.com/manpages...et-edid.1.html
    https://ubuntuforums.org/showthread....8#post10925558

    That Graphics Resolution Sticky has been there for almost 12 years now, and this is why it is still there and still relevant. (LOL)
    Last edited by MAFoElffen; May 13th, 2023 at 04:29 PM.

    "Concurrent coexistence of Windows, Linux and UNIX..." || Ubuntu user # 33563, Linux user # 533637
    Sticky: Graphics Resolution | UbuntuForums 'system-info' Script | Posting Guidelines | Code Tags

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