amd-bc250-docs/docs/linux/kernel.md

Kernel Requirements and Configuration

The Linux kernel version and configuration is critical for BC-250 stability and performance.

Kernel Version Compatibility

Recommended Kernels

Best Compatibility:

• 6.15.7 - 6.17.7 - Full BC-250 support, best performance
• 6.16.x - All versions work well

Stable Fallback:

• 6.12.x LTS - Older but reliable
• 6.13.x - Stable
• 6.14.x LTS - Well-tested

Confirmed Working Versions:

• 6.16.5 (Fedora 42/43)
• 6.15.11-1-lts (Arch Linux)
• 6.17.4 (CachyOS)

!!!success "Current Recommendation" Use kernels 6.15.7 through 6.17.7 for the best BC-250 experience. Kernel support was significantly improved starting with 6.15.7.

Broken Kernels

!!!danger "Avoid These Kernel Versions" - 6.15.0 - 6.15.6: GPU initialization fails - 6.17.8 and newer: GPU driver broken again

These versions cause:
- Kernel panics on boot
- GPU fails to initialize
- `amdgpu: Failed to get gpu_info firmware` error
- Black screen after boot

Known Error Messages:

[drm:amdgpu_discovery_init [amdgpu]] *ERROR* amdgpu_discovery_init failed
amdgpu 0000:01:00.0: amdgpu: Fatal error during GPU init

Required Kernel Parameters

Basic Parameters (All Installations)

Add these to GRUB configuration:

# Edit GRUB
sudo nano /etc/default/grub

# Add to GRUB_CMDLINE_LINUX_DEFAULT:
GRUB_CMDLINE_LINUX_DEFAULT="quiet amdgpu.sg_display=0"

Parameter Explanations:

• quiet - Reduces boot messages (optional)
• amdgpu.sg_display=0 - Required for kernels < 6.10 - disables scatter-gather display

!!!info "amdgpu.sg_display" This parameter is only needed for kernels older than 6.10. If using 6.11+, it doesn't hurt to leave it, but it's not strictly necessary.

Performance Parameters (Optional)

# For maximum gaming performance
GRUB_CMDLINE_LINUX_DEFAULT="quiet amdgpu.sg_display=0 mitigations=off"

Performance Impact of mitigations=off:

• +18 FPS in Cyberpunk 2077 (60 → 78 FPS at 1080p high settings)
• Reduces CPU overhead from Spectre/Meltdown mitigations
• Security trade-off: Disables CPU vulnerability mitigations

!!!warning "Security vs Performance" mitigations=off improves performance but reduces security. Only use on gaming-only systems, not for systems handling sensitive data.

Memory Allocation Parameters (Advanced)

For maximum GPU memory access (14.5-14.75GB):

# Add to kernel parameters
amdgpu.gttsize=14750 ttm.pages_limit=3776000 ttm.page_pool_size=3776000

!!! danger "Do NOT Enable IOMMU" NEVER use amd_iommu=on - IOMMU is broken on BC-250 and causes crashes and display failures. The memory parameters above work WITHOUT enabling IOMMU.

Purpose:

• Allows GPU to access more system RAM
• Useful for VRAM-heavy workloads
• Alternative to increasing BIOS VRAM allocation

Via modprobe (alternative method):

# Create /etc/modprobe.d/increase_amd_memory.conf
sudo nano /etc/modprobe.d/increase_amd_memory.conf

# Add:
options ttm pages_limit=3776000 page_pool_size=3776000
options amdgpu gttsize=14750

# Rebuild initramfs
sudo dracut --regenerate-all --force  # Fedora
sudo mkinitcpio -P  # Arch

Installation Parameter (Temporary)

nomodeset - Use during installation only:

# Add temporarily at GRUB menu (press 'e' to edit)
nomodeset

Purpose: Disables GPU driver, allows booting with basic graphics

!!!danger "Remove After Installation" After installing Mesa drivers, remove nomodeset from GRUB. Leaving it prevents GPU acceleration.

Applying Kernel Parameters

Fedora/RHEL

# Edit GRUB config
sudo nano /etc/default/grub

# Update GRUB
sudo grub2-mkconfig -o /boot/grub2/grub.cfg

# Reboot
sudo reboot

Debian/Ubuntu

# Edit GRUB config
sudo nano /etc/default/grub

# Update GRUB
sudo update-grub

# Reboot
sudo reboot

Arch Linux

# Edit GRUB config
sudo nano /etc/default/grub

# Update GRUB
sudo grub-mkconfig -o /boot/grub/grub.cfg

# Reboot
sudo reboot

Temporary Boot Parameters

To test parameters without permanently changing configuration:

1. Reboot system
2. At GRUB menu, press e to edit boot entry
3. Find line starting with linux or linuxefi
4. Add parameters to end of line
5. Press Ctrl+X to boot with modified parameters

Kernel Management

Checking Current Kernel

# Display kernel version
uname -r

# Example output: 6.14.4-104.fc42.x86_64

Installing Specific Kernel Version

Fedora:

# List available kernels
dnf list kernel --showduplicates

# Install specific version
sudo dnf install kernel-6.14.4-104

# Set as default in GRUB if needed
sudo grub2-set-default "Fedora Linux (6.14.4-104)"

Arch Linux:

# Install LTS kernel
sudo pacman -S linux-lts linux-lts-headers

# Set as default in bootloader

Holding Kernel Version

To prevent automatic updates to problematic kernel versions:

Fedora:

# Install versionlock plugin
sudo dnf install python3-dnf-plugin-versionlock

# Lock kernel at current version
sudo dnf versionlock add kernel

# List locked packages
sudo dnf versionlock list

# Remove lock
sudo dnf versionlock delete kernel

Arch Linux:

# Edit pacman.conf
sudo nano /etc/pacman.conf

# Add under [options]:
IgnorePkg = linux

# Save and exit

Debian:

# Hold kernel package
sudo apt-mark hold linux-image-6.14.11-amd64

# Unhold
sudo apt-mark unhold linux-image-6.14.11-amd64

Removing Broken Kernel

If kernel 6.15.0-6.15.6 or 6.17.8+ was installed and causes issues:

Fedora:

# Boot into working kernel from GRUB menu
# Remove broken kernel (example: 6.17.8)
sudo dnf remove kernel-6.17.8\*

# Or remove all 6.17.8+ kernels
sudo dnf remove 'kernel-6.17.[8-9]*' 'kernel-6.17.1[0-9]*'

# Verify removal
dnf list installed kernel

Arch Linux:

# Boot into working kernel
# Remove problematic kernel
sudo pacman -R linux  # if on broken version

# Install known-good kernel
sudo pacman -S linux-lts  # 6.12 or 6.14 LTS
# or
sudo pacman -S linux  # check version is 6.15.7-6.17.7

Kernel Patches for BC-250

GPU Frequency Range Patch

Purpose: Enables extended frequency range (350 MHz - 2230 MHz) instead of default (1000-2000 MHz)

Distributions with Patch Included:

• Bazzite (pre-applied)
• PikaOS (pre-applied)

Manual Patching:

Required for:

• Fedora
• Arch Linux
• Debian
• Other distributions

Patch Application (Advanced):

1. Download BC-250 frequency patch
2. Apply to kernel source
3. Compile custom kernel
4. Install and boot

[Detailed patching guide available in community resources]

Alternative: Use distributions with patch pre-applied (Bazzite, PikaOS)

TKG Kernel (Arch-based)

For Arch users, linux-tkg provides easy custom kernel building:

git clone https://github.com/Frogging-Family/linux-tkg
cd linux-tkg

# Create patch directory
mkdir linux612-tkg-userpatches

# Place BC-250 patch in directory

# Run installer
./install.sh install

# Select Linux 6.12 LTS during setup

Benefits:

• Easy kernel customization
• Includes performance optimizations
• BC-250 patch integration

Compilation Time:

• Full compile: ~45 minutes
• With modprobed-db: ~8 minutes

Kernel Troubleshooting

GPU Not Detected After Kernel Update

Symptoms:

• Black screen after boot
• lspci | grep VGA shows device but driver not loading
• dmesg | grep amdgpu shows errors

Solution:

1. Boot into older kernel from GRUB (hold Shift at boot)
2. Remove newer kernel
3. Hold kernel version
4. Report issue to distribution

System Boots But No GPU Acceleration

Check:

# Is amdgpu module loaded?
lsmod | grep amdgpu

# Check for errors
dmesg | grep -i amdgpu

# Verify rendering
glxinfo | grep "OpenGL renderer"
# Should NOT show "llvmpipe"

Possible Causes:

• nomodeset still in GRUB config
• Missing kernel parameters
• Mesa not installed

Kernel Panic on Boot

Symptoms:

• System crashes during boot
• Kernel panic message

Most Common Cause: Kernel 6.15.0-6.15.6 or 6.17.8+

Solution:

1. Boot into working kernel (hold Shift, select previous kernel)
2. Remove problematic kernel version
3. Lock kernel version to prevent auto-update

Kernel Version Matrix

Kernel Version	Status	Notes
6.10.x	⚠️ Works	amdgpu.sg_display=0 required
6.11.x	✅ Good	Mesa 25.1+ required
6.12.x LTS	✅ Good	Stable fallback
6.13.x	✅ Good	Stable
6.14.x LTS	✅ Good	Well-tested
6.15.0-6.15.6	❌ Broken	GPU init fails
6.15.7-6.15.x	✅ Recommended	Kernel support fixed
6.16.x	✅ Recommended	Full compatibility
6.17.0-6.17.7	✅ Recommended	Best support
6.17.8+	❌ Broken	GPU driver broken again

See Also

• Mesa Driver Installation
• Distribution Comparison
• System Configuration
• Troubleshooting Guide