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Display Connectivity

Guide to connecting displays to the BC-250 and troubleshooting display issues.

Display Output Overview

Available Connectors

  • DisplayPort: 1x full-size DisplayPort 1.4
  • HDMI: None (requires adapter)
  • Resolution Support: Up to 4K @120Hz
  • HDR Support: Yes (HDR10)

DisplayPort Only

The BC-250 only has DisplayPort output. For HDMI displays, you'll need a DP to HDMI adapter.

DisplayPort Direct Connection

DisplayPort Cable: - Version: DisplayPort 1.4 certified - Length: 1-2m (longer cables can cause issues) - Quality: Use certified cables (VESA DP certified)

Resolution Support: - 1920x1080 (1080p) @ 144Hz+ - 2560x1440 (1440p) @ 144Hz+ - 3840x2160 (4K) @ 120Hz

Native DisplayPort Recommended

If your monitor has DisplayPort, use it directly. This avoids adapter compatibility issues.

Audio Over DisplayPort

Status: Works for most users

Confirmed Working Monitors: - MSI 27CQ6F (direct DP connection) - Various Dell/HP monitors - Most modern DisplayPort monitors

Configuration: 

# Check audio devices
aplay -l

# Select HDMI/DisplayPort audio in system settings
# Usually appears as "HDMI/DisplayPort" or "AMD/ATI"

Troubleshooting Audio: - Some monitors don't pass through audio - Check monitor specs for audio support - Verify speakers are enabled on monitor - Test with headphones/external speakers first

DP to HDMI Adapters

Adapter Types

Passive Adapters (Recommended): - Audio: Usually works reliably - Cost: Inexpensive ($5-10) - Use Case: Most users, TV connections - Note: DP 1.2 max (1440p @60Hz, some support 1440p @165Hz)

Active Adapters: - Audio: Silent or slow on older kernels. Caused by a kernel bug in the DisplayPort audio clock, not by the adapter, and fixed by a kernel update - Cost: More expensive ($15-30) - Use Case: 4K @60Hz+ on HDMI displays, HDMI-CEC - Issues: Check your kernel against the audio page before writing the adapter off

Known Issues with Adapters

The adapters were never the problem

The "adapters break audio" reports trace back to a kernel bug: older kernels program the DisplayPort audio clock for a reference clock the hardware does not have. Active adapters are real DisplayPort sinks, so they receive that off-spec audio stream and often refuse to lock (silence). Passive adapters make the driver use a different, unaffected clock path, which is why they seem immune. Kernel 7.2 and newer fix it completely, and current longterm kernels fix the large error. See DisplayPort Audio: Silence, Desync or Slow Pitch for which kernels are affected, the mechanism and a workaround for older ones.

Common Symptoms: - Display works, no audio (active adapters: the sink refuses the off-spec stream) - Audio plays but slow, out of sync, or with periodic crackle (sinks that tolerate it) - Audio dropouts/clicking

Workarounds: 1. Update to a kernel with the DP audio clock fix, which fixes audio through the adapter you already have (the audio page also has a workaround for older kernels) 2. Use a passive adapter (unaffected clock path, but 1080p/1440p limits and no CEC) 3. Use USB audio adapter/DAC 4. Use Bluetooth audio

Tested Adapter Compatibility

Adapter Type Display Works Audio Works Notes
UGREEN 8K Active (Realtek RTD2173) Yes Yes, with the DP audio clock fix Silent without the fix. Verified at 4K60 and 1080p120; HDMI-CEC works. Tested by @Weijtmans
Generic Passive Usually Sometimes Hit or miss
Cable Matters Active Yes No 4K works, no audio
Club3D Active Yes Yes, with the DP audio clock fix Silent without the fix. Verified at 4K120. Tested by @GabMus
StarTech Active Yes No Reliable display, no audio

The 'No audio' rows predate the root cause discovery

The Cable Matters/StarTech results were collected before the DP audio clock bug was identified. The mechanism predicts they fail for the same reason and work on a kernel with the fix, but that has not been re-tested. If you own one, re-test on a current kernel and report back with the output of uname -r.

Common Display Problems

No Display on Boot

Symptoms: - Monitor shows "No Signal" - System appears to be running (fans spin) - Power LED on board is lit

Causes: 1. No GPU drivers installed 2. Incorrect kernel parameters 3. Bad cable/adapter 4. Monitor incompatibility

Solutions:

Step 1: Boot with nomodeset 

# At GRUB, press 'e' to edit boot entry
# Find line starting with 'linux' or 'linuxefi'
# Add 'nomodeset' to end of line
# Press Ctrl+X to boot

Step 2: Verify cable/adapter - Try different DisplayPort cable - Try display on another system - Remove adapter if using one

Step 3: Check BIOS settings - Verify display output is enabled - Try resetting BIOS to defaults

See Display Troubleshooting Guide for detailed steps.

Black Screen After Login

Symptoms: - GRUB menu displays - Login screen displays - Black screen after logging in

Cause: Desktop environment issue, usually Wayland

Solutions:

Option 1: Switch to X11 1. At login screen, select user 2. Click gear icon (bottom right) 3. Select "GNOME on Xorg" or "Plasma (X11)" 4. Log in

Option 2: Disable Wayland 

# Edit GDM config
sudo nano /etc/gdm/custom.conf

# Uncomment this line:
WaylandEnable=false

# Save and reboot

Display Works But Low Resolution

Symptoms: - Display detected but stuck at 1024x768 or 1920x1080 - Higher resolutions not available - Refresh rate limited to 60Hz

Causes: - GPU drivers not loaded - Using software rendering (llvmpipe) - Bad cable limiting bandwidth

Check Current Driver: 

glxinfo | grep "OpenGL renderer"
# Should show: AMD Radeon Graphics (RADV GFX1013)
# If shows: llvmpipe - drivers not working

Solutions: 1. Install Mesa 25.1+ drivers 2. Remove nomodeset from GRUB 3. Use certified DisplayPort cable 4. Update monitor firmware

See Mesa Installation Guide

Flickering or Artifacts

Symptoms: - Screen flickers occasionally - Visual artifacts (lines, blocks) - Colors incorrect

Causes: - Bad cable - Interference - Overclocking too high - Insufficient cooling

Solutions: 1. Replace DisplayPort cable 2. Reduce GPU overclock 3. Check GPU temperature 4. Try different monitor input

HDMI 2.1 / 4K @120Hz Issues

Limitation: DP to HDMI adapters often limited to HDMI 2.0

HDMI 2.0 Limits: - 4K @ 60Hz - No 4K @ 120Hz - Limited HDR

HDMI 2.1 Requirement: - Requires active DP 1.4 to HDMI 2.1 adapter - Still may have compatibility issues

Use Native DisplayPort

For high refresh rate 4K gaming, use a native DisplayPort monitor instead of adapter.

HDMI-CEC Through Active Adapters

The BC-250 can join an HDMI-CEC bus (TV power on/off, input switching, TV-remote control) even though it has no HDMI port: a CEC-capable active DP-to-HDMI adapter tunnels CEC over the DisplayPort AUX channel, and the mainline kernel picks it up (CONFIG_DRM_DISPLAY_DP_AUX_CEC). No extra hardware, no Pulse-Eight dongle.

Verified working: UGREEN 8K active DP-HDMI adapter (Realtek RTD2173). /dev/cec0 appears, the board registers as a CEC 2.0 Playback Device (logical address 8), and traffic is bidirectional: the TV answers a power-status query in 87 ms and an OSD-name query in 29 ms. Tested by @Weijtmans on Bazzite (Fedora Atomic 43), kernel 6.17.7-ba29, Samsung TV.

The kernel's CEC adapter list is not a compatibility matrix, and neither is /dev/cec0

The kernel documentation lists the adapters its CEC maintainer has seen work (Parade PS175/PS176/PS186 and MegaChips 2900 chipsets, a few Club3D, CableCreation and HP models). It is a list of observations: the RTD2173 is not on it and works. The same documentation also warns that many adapters with a tunnelling-capable chip never connect the CEC pin, and on those /dev/cec0 still appears but never sees the TV. So do not rule an adapter out because it is not listed, and do not rule it in because /dev/cec0 exists: the test is whether the TV answers, see the quick start below.

Passive adapters cannot do CEC; the kernel documentation says so too. Tunnelling is advertised in a DPCD register (0x3000) that only a real DP sink such as an active adapter implements, and the kernel creates /dev/cec0 only when bit 0 of it is set. You can read it directly:

sudo dd if=/dev/drm_dp_aux0 bs=1 skip=$((0x3000)) count=1 2>/dev/null | xxd
# 01, 03, 05 or 07 (bit 0 set) = the adapter advertises CEC tunnelling
# 00, or no output = no tunnelling (a passive adapter gives no output)

Advertising tunnelling is necessary, not sufficient; see the note above.

Quick start (cec-ctl is in v4l-utils):

ls /dev/cec*
# Should show: /dev/cec0

cec-ctl -d /dev/cec0 --playback   # register as a Playback device on the bus
cec-ctl -d /dev/cec0 -S           # scan: shows the TV, audio system, other devices

The scan must list at least one device besides the BC-250 itself. If it shows only the BC-250, either the adapter does not connect the CEC pin or CEC is switched off for that input on the TV.

/dev/cec0 is owned root:video, so add your user to the video group for non-root use, and remember group changes only apply to new logins.

On Bazzite and other ostree distros, usermod -aG silently does nothing

On an ostree system with nss-altfiles, the video group often exists only in the read-only /usr/lib/group, with no line in /etc/group. usermod -aG video $USER then validates the group through NSS, edits /etc/group, finds no line to append to, and exits 0 without changing anything. Seed the group line first, then add the member:

grep '^video:' /usr/lib/group | sudo tee -a /etc/group
sudo gpasswd -a $USER video

Tested by: @Weijtmans. BC-250, Bazzite (Fedora Atomic 43), kernel 6.17.7-ba29.

Naming the Box on the CEC Bus

On the kernel-CEC path a device announces itself with cec-ctl's default OSD name unless --osd-name is passed, so the TV's source list shows the box as "Playback". Two Bazzite pitfalls stack on top of that:

  • Setting CEC_OSD_NAME in /etc/default/cec-control is a no-op here. cec-control builds --osd-name into its argument list but only uses that list on its libcec code path; on the /dev/cec0 path, the one the BC-250 takes, it runs a bare cec-ctl -d "$CEC_DEVICE" --playback.
  • cec-onboot.service re-runs that bare registration on every boot, clobbering any name set by hand.

Set the name directly (CEC limits OSD names to 14 characters), and reapply it after cec-onboot if you want it to survive reboots:

cec-ctl -d /dev/cec0 --playback --osd-name "Steam Machine"

bc250-cec-identity.sh does this and can install a small unit that makes the name persistent; bc250-cec-check.sh from the same repo proves whether the TV actually answers on the bus.

Renaming changes the name, not the device category: CEC has no game-console device type, and amdgpu implements no ALLM, so a TV will not switch into Game Mode by itself. Label the input as a game console in the TV's own source menu for that.

Tested by: @Weijtmans. BC-250, Bazzite (Fedora Atomic 43), kernel 6.17.7-ba29, Samsung TV.

Multiple Display Support

Limitations

Hardware: - Only 1 physical DisplayPort output - No multi-monitor support from single board

Options for Multiple Displays:

Option 1: USB DisplayLink Adapter - Add USB to HDMI/DisplayPort adapter - Works for desktop use (plug in after boot for best results) - Not suitable for gaming — high latency due to CPU-based compression, BC-250's CPU is the bottleneck - Does not work in Steam Deck game mode

Option 2: DisplayPort MST Hub - Split single DP into multiple displays - Maximum 2 screens via MST on BC-250 - Shares bandwidth between displays - Works for productivity - Limited resolution per display

Tested MST Hubs Compatibility

Adapter Display-out DP Version Display Works Audio Works Notes
StarTech MST14DP122DP DP (2) 1.4 Yes Yes Worked consistently with different monitors and DP cables
Monoprice 21972 DP (2) 1.2 Mirror only Yes Was only able to get displays to mirror
ENBUER DP (2) 1.2? Mirror only Yes Was only able to get displays to mirror
Generic HDMI (2) N/A No No No audio or video output

Option 3: Multiple BC-250 Boards - Use separate board per monitor - Impractical for most users

Display Configuration

Setting Resolution and Refresh Rate

KDE Plasma: 1. System Settings → Display and Monitor 2. Select your display 3. Choose resolution and refresh rate 4. Apply

GNOME: 1. Settings → Displays 2. Select resolution from dropdown 3. Click Apply

Command Line (xrandr): 

# List available modes
xrandr

# Set mode
xrandr --output DisplayPort-0 --mode 1920x1080 --rate 144

Custom Resolutions

Some monitors may require custom modelines:

# Generate modeline
cvt 2560 1440 144

# Add to xrandr
xrandr --newmode "2560x1440_144.00" ...
xrandr --addmode DisplayPort-0 "2560x1440_144.00"

HDR Configuration

HDR support in Linux is improving but still experimental:

Check HDR Support: 

# KDE Plasma 6+: HDR toggle in display settings
# GNOME: Limited HDR support

Notes: - HDR support varies by desktop environment - KDE Plasma 6+ has best HDR support - May require Wayland session - Game-specific HDR may not work

Audio Solutions

Audio through DP-HDMI adapters works on a current kernel, see DisplayPort Audio. If you are stuck on an older kernel or want a separate audio output anyway, here are alternative solutions:

Option 1: USB Audio Adapter

Recommended Adapters: - Creative Sound Blaster Play! 4 - Sabrent USB Audio Adapter - FiiO K3 DAC (audiophile option)

Setup: 1. Plug USB audio adapter into BC-250 USB port 2. Connect speakers/headphones to adapter 3. Select USB audio device in system settings

Option 2: Bluetooth Audio

Requirements: - USB Bluetooth adapter - Bluetooth speakers/headphones

Setup: 

# Install Bluetooth tools
sudo dnf install bluez bluez-tools  # Fedora
sudo pacman -S bluez bluez-utils    # Arch

# Enable Bluetooth
sudo systemctl enable --now bluetooth

# Pair device (use GUI or bluetoothctl)

Latency Warning: Bluetooth adds ~100-200ms latency, noticeable in gaming

Option 3: Monitor with Displayport + Speakers

If your monitor has DisplayPort input AND built-in speakers: - Audio over DisplayPort usually works - Check monitor supports audio input - Enable speakers in monitor settings

Troubleshooting Checklist

Before Asking for Help

  1. Verify hardware:
  2. Cable is securely connected both ends
  3. Monitor works with another device

  4. Power LED on monitor is lit

  5. Check software: 

    # GPU detected?
lspci | grep VGA

# Driver loaded?
lsmod | grep amdgpu

# Mesa version?
glxinfo | grep "OpenGL version"

  6. Test with nomodeset:

  7. If display works with nomodeset, driver issue

  8. If no display with nomodeset, hardware issue

  9. Try different cable/adapter:

  10. Cables can fail

  11. Adapters have compatibility issues

  12. Check logs: 

    # Check for errors
dmesg | grep -i amdgpu
journalctl -b | grep -i drm

Display Recommendations by Use Case

Gaming @ 1080p 144Hz

  • Display: Any 1080p 144Hz+ DisplayPort monitor
  • Cable: DP 1.4 certified cable
  • Expected: Works flawlessly

Gaming @ 1440p 144Hz

  • Display: 1440p 144Hz+ DisplayPort monitor
  • Cable: DP 1.4 certified, <2m length
  • Expected: Works well

4K @ 60Hz

  • Display: 4K 60Hz monitor with DisplayPort OR HDMI
  • Cable: DP 1.4 cable OR active DP-to-HDMI adapter
  • Audio: Use USB audio if adapter needed

4K @ 120Hz

  • Display: 4K 120Hz DisplayPort monitor
  • Cable: DP 1.4 certified cable
  • Note: May need to manually set 120Hz in settings

TV Connection (Living Room Gaming)

  • Display: 4K TV with HDMI 2.0+
  • Adapter: Active DP to HDMI 2.0 adapter
  • Audio: TV speakers / soundbar over the adapter works on a kernel with the DP audio clock fix; Bluetooth/USB audio as fallback
  • Note: Test adapter audio before permanent setup

See Also