Only One Monitor (Cable) Showing Up in Display Settings: A Comprehensive Troubleshooting Guide

At revWhiteShadow, we understand the frustration of encountering display issues, especially when trying to maximize your monitor’s capabilities. It’s particularly annoying when your system fails to recognize a monitor connection entirely, limiting you to a single display or restricting refresh rates. This guide, crafted by revWhiteShadow, aims to provide a detailed and methodical approach to resolving the issue where only one monitor (cable) is detected in your display settings, focusing primarily on scenarios involving HDMI and DisplayPort (DP) connections under Linux-based systems like Linux Mint.

Understanding the Problem: HDMI vs. DisplayPort and Refresh Rate Limitations

The situation described – where an HDMI connection is limited to 60Hz while a DisplayPort connection should unlock higher refresh rates like 144Hz – is a common one. Several factors can contribute to this discrepancy, ranging from cable limitations to driver issues and system configuration quirks. The initial appearance of both monitors after a fresh Linux Mint install, followed by the disappearance of the DisplayPort-connected monitor, suggests a software configuration problem, rather than a hardware failure.

Common Causes for Monitor Detection Issues

  • Driver Problems: Incorrect, outdated, or corrupted graphics drivers are frequently the root cause of display detection problems.
  • Cable Limitations: Not all HDMI or DisplayPort cables are created equal. Older cable versions may not support the bandwidth required for higher resolutions and refresh rates.
  • Monitor Settings: The monitor itself might have settings that limit the input signal or refresh rate.
  • Operating System Configuration: The display settings in your operating system (Linux Mint in this case) may not be correctly configured to detect and utilize both monitors.
  • Graphics Card Compatibility: In rare cases, specific graphics cards may have compatibility issues with certain monitors or connection types.
  • X Server Configuration: The X server in Linux handles graphical display. Configuration errors can cause detection issues.
  • DisplayPort Deep Sleep: A DisplayPort feature where the port goes into a low power sleep mode. It can cause issues when waking up.

Troubleshooting Steps: A Systematic Approach

We will go through a step-by-step troubleshooting process to try and resolve the issue where only the HDMI monitor is being detected. Work through these steps in order, testing after each step to see if the problem is resolved.

1. Verify Basic Connections and Hardware

Before diving into software configurations, ensure the basics are covered.

  • Cable Integrity: Inspect both the HDMI and DisplayPort cables for any physical damage. Try swapping the cables with known working ones to rule out a faulty cable.
  • Port Functionality: Test both the HDMI and DisplayPort ports on your graphics card and monitor by swapping the cables between them. If one port consistently fails to detect a signal, it may be defective.
  • Monitor Power and Input: Confirm that both monitors are powered on and set to the correct input source (HDMI or DisplayPort). Cycle through the input options on the monitor’s OSD (On-Screen Display) to ensure the correct one is selected.
  • Direct Connection: Avoid using adapters or converters initially. Connect the monitors directly to the graphics card using the appropriate cables. Adapters can sometimes introduce compatibility issues.
  • BIOS/UEFI Settings: Some systems have BIOS/UEFI settings related to display priority or graphics card initialization. Consult your motherboard’s manual to ensure these settings are configured correctly. Often, there are options related to integrated graphics that can interfere with discrete graphics cards.
  • Check other Operating Systems/Live Media: As a way of sanity check, boot up other operating systems and see if the same symptoms persist. If the issue does not persist, then it might have to do with your current installation.

2. Investigate Driver Issues (Most Likely Culprit)

Graphics drivers are a common source of monitor detection problems.

  • Identify Your Graphics Card: Determine the exact model of your graphics card (e.g., NVIDIA GeForce RTX 3080, AMD Radeon RX 6800 XT). You can usually find this information in your system settings or by using a command-line tool like lspci | grep VGA in Linux.
  • Update Drivers: Install the latest stable drivers for your graphics card.
    • NVIDIA: Use the NVIDIA driver manager tool (usually included with the driver package) or download the drivers directly from the NVIDIA website. In Linux, you can often use the nvidia-driver-<version> packages available in your distribution’s repositories.
    • AMD: Download the drivers from the AMD website or use the AMD driver manager tool. Similar to NVIDIA, Linux distributions often provide AMD drivers through their package managers.
    • Intel: Intel graphics drivers are typically included with the operating system, but it’s still a good idea to check for updates on the Intel website or through your distribution’s package manager.
  • Reinstall Drivers: Sometimes, a driver update can cause problems. Try completely uninstalling the existing drivers (using a tool like apt purge nvidia-* for NVIDIA drivers on Debian/Ubuntu-based systems) and then reinstalling the latest version.
  • Consider Proprietary vs. Open-Source Drivers: In Linux, you often have a choice between proprietary (e.g., NVIDIA’s proprietary drivers) and open-source drivers (e.g., Nouveau for NVIDIA cards, AMDGPU for AMD cards). Proprietary drivers generally offer better performance and compatibility, but open-source drivers may be more stable in some cases. Experiment with both to see which works best for your setup.
  • Kernel Updates: A recent Linux kernel update can sometimes introduce incompatibilities with graphics drivers. Try booting into an older kernel version (if available) to see if that resolves the issue.

3. Linux Mint Display Settings Configuration

Linux Mint uses X Server to manage graphics, and the display settings provide a graphical interface to configure your monitors.

  • Access Display Settings: Open the “Display” settings in Linux Mint (usually found in the system settings menu).
  • Detect Displays: Look for a “Detect Displays” or “Identify Displays” button. Click it to force the system to rescan for connected monitors.
  • Arrangement: If both monitors are detected but not arranged correctly, drag and drop them in the display settings to match your physical setup.
  • Resolution and Refresh Rate: Ensure that each monitor is set to its optimal resolution and refresh rate. The DisplayPort-connected monitor should be set to 144Hz (or higher, if supported).
  • Primary Display: Designate one of the monitors as the primary display. This is where the desktop icons and taskbar will appear.
  • Mirroring vs. Extending: Choose whether to mirror the displays (show the same content on both monitors) or extend the desktop (treat both monitors as a single, larger workspace). Choose “Extend displays” for independent use.
  • Save Configuration: Apply the changes and save the configuration.

4. X Server Configuration (Advanced)

If the graphical display settings don’t resolve the issue, you may need to manually configure the X Server. This requires editing configuration files, so proceed with caution.

  • xrandr Command: The xrandr command is a powerful tool for configuring displays from the command line. Open a terminal and run xrandr to see a list of connected monitors and their available resolutions and refresh rates.
  • Creating an xorg.conf File: If an xorg.conf file doesn’t exist (it’s not always required in modern Linux systems), you can create one. This file allows you to specify detailed configuration options for the X Server.
    • sudo Xorg -configure :1 -screen 0 (This command will generate a basic configuration file. It may disable your current display temporarily.)
    • sudo mv xorg.conf.new /etc/X11/xorg.conf
    • Edit the xorg.conf file using a text editor (e.g., sudo nano /etc/X11/xorg.conf). Pay close attention to the “Device” and “Monitor” sections. Ensure that the correct drivers are specified and that the monitor settings (resolution, refresh rate) are configured correctly.
  • Modelines: For specific refresh rates and resolutions, you may need to add “Modeline” entries to the xorg.conf file. You can generate Modelines using online tools or by consulting your monitor’s manual.
  • Example xorg.conf Snippet:
Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"  # Or "amdgpu" or "intel"
    VendorName     "NVIDIA Corporation" # or "AMD" or "Intel"
    BoardName      "GeForce RTX 3080"  # Replace with your card
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    ModelName      "Your Monitor Model" #Replace with your monitor model
    HorizSync       30-165
    VertRefresh     24-144
    Option         "PreferredMode" "2560x1440_144" # Replace with desired resolution and refresh
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    SubSection     "Display"
        Depth       24
        Modes      "2560x1440_144"
    EndSubSection
EndSection
  • Restart X Server: After making changes to the xorg.conf file, restart the X Server to apply the changes. This can usually be done by logging out and logging back in, or by restarting the display manager (e.g., sudo systemctl restart lightdm for LightDM).

5. DisplayPort Deep Sleep Workaround

DisplayPort has a feature called “Deep Sleep” which can sometimes cause detection issues.

  • Disable Deep Sleep (if possible): Some monitors have an option in their OSD menu to disable DisplayPort Deep Sleep. Check your monitor’s manual for instructions.
  • Kernel Parameter: You can try adding a kernel parameter to disable DisplayPort Deep Sleep.
    • Edit the /etc/default/grub file: sudo nano /etc/default/grub
    • Add drm_dp_mst=0 to the GRUB_CMDLINE_LINUX_DEFAULT line (e.g., GRUB_CMDLINE_LINUX_DEFAULT="quiet splash drm_dp_mst=0").
    • Update GRUB: sudo update-grub
    • Reboot your system.

6. EDID (Extended Display Identification Data) Issues

EDID is data that a monitor sends to the graphics card to identify itself and its capabilities. Sometimes, this data can be corrupted or misinterpreted.

  • EDID Override: You can try overriding the EDID data with a custom EDID file. This is an advanced technique and should be done with caution.
    • Extract EDID: Use a tool like get-edid to extract the EDID data from your monitor.
    • Modify EDID (if necessary): You can use an EDID editor to modify the EDID data, but this is generally not recommended unless you know what you’re doing.
    • Load EDID: Configure the X Server to load the custom EDID file. This typically involves adding a " секция" to the xorg.conf file.

7. Check Power Supply and System Resources

Insufficient power or resource contention can sometimes cause display issues.

  • Power Supply: Ensure that your power supply has sufficient wattage to support your graphics card and other components, especially if you’re running multiple monitors.
  • System Load: Monitor your system’s CPU and GPU usage. High CPU or GPU load can sometimes interfere with display detection.

8. Kernel Modules and DKMS

Dynamic Kernel Module Support (DKMS) helps manage kernel modules, including graphics drivers, so they can be automatically rebuilt when the kernel is updated.

  • Verify DKMS Installation: Ensure that DKMS is installed on your system.
  • Rebuild Drivers: Try rebuilding the graphics drivers using DKMS: sudo dkms autoinstall

9. Investigate the system logs

System logs often contain valuable information about hardware detection and driver initialization.

  • /var/log/Xorg.0.log: This log file contains information about the X server, including any errors or warnings related to display detection.
  • /var/log/syslog or /var/log/messages: These logs contain general system messages and can provide clues about hardware initialization and driver loading.

Use tools like grep to search for relevant keywords in the logs, such as “HDMI,” “DisplayPort,” “EDID,” “driver,” or “error.”

Specific Troubleshooting for HDMI 60Hz Limitation

If your HDMI connection is consistently limited to 60Hz, even after updating drivers and configuring display settings, consider the following:

  • HDMI Cable Version: Ensure that your HDMI cable supports HDMI 2.0 or higher, which is required for 4K resolution at 60Hz or 1080p/1440p at higher refresh rates. Older HDMI cables may be limited to lower bandwidth.
  • Monitor HDMI Version: Check your monitor’s specifications to see what version of HDMI it supports. Some monitors may have only one HDMI port that supports higher refresh rates.
  • Graphics Card HDMI Version: Similarly, check your graphics card’s specifications to see what version of HDMI it supports.
  • Custom Resolution: In some cases, you may need to create a custom resolution in the NVIDIA Control Panel or AMD Radeon Settings to force the HDMI connection to use a higher refresh rate.

Conclusion: Persistence is Key

Troubleshooting display issues can be a complex and time-consuming process. Remember to approach the problem systematically, testing after each step to see if the issue has been resolved. By following the steps outlined in this guide, you should be able to identify and resolve the problem of only one monitor (cable) showing up in your display settings, and unlock the full potential of your multi-monitor setup. At revWhiteShadow, we are committed to providing comprehensive and reliable solutions to your technical challenges. Good luck!