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Boot Troubleshooting Guide

Complete guide to diagnosing and fixing boot issues on the BC-250. This covers everything from black screens during installation to kernel panics and bootloader problems.

Quick Diagnosis Flowchart

Start here to identify your issue:

  1. Does the board power on? (Fan spins, LED lights up)
  2. NO → See Hardware Issues

  3. YES → Continue to #2

  4. Can you see BIOS menu? (Press Del during boot)

  5. NO → See Hardware Issues

  6. YES → Continue to #3

  7. What happens when you try to boot?

  8. Black screen during installer → No Display During Installation
  9. Black screen after installation → No Display After Installation
  10. Boots to black screen, no OS → Black Screen After GRUB
  11. System hangs/freezes during boot → Boot Hangs
  12. Kernel panic or error messages → Kernel Panics
  13. GRUB not appearing → GRUB/Bootloader Issues

No Display During Installation

Problem: Black Screen When Booting Installer

Symptoms: - USB boots, but screen goes black - No installer appears - Monitor shows "No Signal" - Works in BIOS but not in installer

Cause: Installer doesn't have BC-250 GPU drivers. The Linux framebuffer (KMS) attempts to initialize the GPU and fails, resulting in no display.

Solution: Use nomodeset Parameter

Fedora: Use Basic Graphics Mode

In Fedora installer boot menu:

  1. Select "Troubleshooting"
  2. Choose "Install in Basic Graphics Mode"

This enables nomodeset automatically.

Manual Method (Any Distro)

  1. At GRUB boot menu, press e to edit boot entry
  2. Find the line starting with linux or linuxefi
  3. Go to the end of that line
  4. Add a space, then type: nomodeset
  5. Press Ctrl+X or F10 to boot

Example: 

# Before:
linux /vmlinuz root=live:CDLABEL=Fedora quiet

# After:
linux /vmlinuz root=live:CDLABEL=Fedora quiet nomodeset

What nomodeset Does

  • Disables kernel mode setting (KMS) - Prevents kernel from initializing GPU
  • Forces fallback to VESA/UEFI framebuffer - Uses basic display mode
  • Allows display without GPU drivers - Works with any GPU
  • Enables installation to proceed - You can complete the install

MUST Remove After Driver Installation

Once Mesa drivers are installed, nomodeset MUST be removed or GPU acceleration won't work. See Removing nomodeset.

No Display After Installation

Problem: Installation Complete But No Display on Boot

Symptoms: - Installation completed successfully - System boots (fan spins, LED lights up, disk activity) - Display shows "No Signal" or stays black - Can't reach login screen

Cause: Same issue as installer - GPU drivers not yet installed. The system attempts to initialize graphics and fails.

Solution Options:

  1. Power on and immediately watch for GRUB menu (appears for 5 seconds)
  2. When GRUB appears, press e to edit
  3. Find the line with linux (usually starts with linux /boot/vmlinuz)
  4. Add nomodeset to the end of that line
  5. Press Ctrl+X to boot

If GRUB doesn't appear: - Try holding Shift (BIOS) or Esc (UEFI) during boot - Or tap the key repeatedly right after BIOS screen

  1. Once booted, install drivers (see distribution guides)
  2. Remove nomodeset permanently (see below)

Option 2: Recovery Mode

Some distributions offer recovery/safe mode with basic graphics:

  1. Select "Advanced options" in GRUB
  2. Choose kernel with "(recovery mode)" suffix
  3. Select "Resume normal boot" with networking
  4. Install drivers once booted
  5. Reboot normally

Option 3: Reinstall with Drivers Pre-Downloaded

  1. Boot installer again with nomodeset
  2. Install OS
  3. Before reboot, chroot into installed system
  4. Install Mesa 25.1+ while still in installer
  5. Reboot without nomodeset

Black Screen After GRUB

Problem: GRUB Shows, Select Entry, Then Black Screen

Symptoms: - GRUB menu appears and works - Select a boot entry - Screen goes black and nothing happens - System seems frozen

Cause: Kernel is loading but can't initialize display due to missing/incompatible drivers.

Immediate Fix:

  1. Reboot and get to GRUB menu
  2. Highlight your boot entry
  3. Press e to edit
  4. Add nomodeset to kernel line
  5. Press Ctrl+X to boot

Long-term Fix:

After booting with nomodeset:

# Check if drivers installed
glxinfo | grep "OpenGL version"
# Should show Mesa 25.1+

# If not installed, install drivers first
# (See distribution-specific guides)

# Then verify kernel version
uname -r
# Should be 6.15.7-6.17.7 (best) or 6.12.x-6.14.x LTS (stable)
# AVOID 6.15.0-6.15.6 and 6.17.8+

If kernel is 6.15.0-6.15.6 or 6.17.8+: 

# Fedora - install working kernel
sudo dnf install kernel-6.16.5-*  # or any 6.15.7-6.17.7 version
# Or for LTS stability:
sudo dnf install kernel-6.14.*

# List available kernels
sudo grubby --info=ALL

# Set working kernel as default
sudo grubby --set-default /boot/vmlinuz-6.16.*

Broken Kernel Versions

Kernel versions 6.15.0-6.15.6 and 6.17.8+ have driver incompatibility with Cyan Skillfish GPUs. Use 6.15.7-6.17.7 for best performance or 6.12.x-6.14.x LTS for stability.

Boot Hangs or Freezes

Problem: System Starts Booting But Hangs

Symptoms: - Boot process starts (text scrolling or logo) - Stops at specific point - No error message, just frozen - Doesn't reach login screen

Common Causes & Solutions:

1. IOMMU Conflicts

Diagnosis: System hangs after "AMD-Vi" messages in boot log.

Solution: Disable IOMMU in BIOS:

  1. Reboot and press Del to enter BIOS
  2. Navigate to Advanced or Chipset Configuration
  3. Find IOMMU or AMD IOMMU
  4. Set to Disabled
  5. Save and exit (F10)

Verify after boot: 

dmesg | grep -i iommu
# Should show: "AMD-Vi: AMD IOMMU disabled"

IOMMU is Broken on BC-250

IOMMU is broken on BC-250 and causes display issues, black screens, and system instability. ALWAYS keep it disabled. Even for virtualization, IOMMU does not work reliably on this board.

2. VRAM Allocation Not Applied

Diagnosis: You set 512MB dynamic VRAM in BIOS but settings didn't stick.

Cause: BIOS settings don't persist after flashing unless CMOS is cleared.

Solution: Clear CMOS:

Method A: Remove Battery 1. Power off completely 2. Unplug power cable 3. Remove CR2032 CMOS battery 4. Wait 60 seconds (or press power button 5 times) 5. Replace battery 6. Power on, enter BIOS 7. Reconfigure VRAM allocation 8. Save and exit

Method B: CMOS Jumper 1. Power off and unplug 2. Locate CLR_CMOS jumper on board 3. Move jumper to clear position (see board pinout) 4. Wait 10 seconds 5. Return jumper to normal position 6. Power on and reconfigure BIOS

This Fixes Most 'Bricked After Flash' Issues

If your board seems dead after BIOS flash, 90% chance clearing CMOS fixes it.

3. Insufficient RAM (ZRAM Conflict)

Diagnosis: System hangs when loading desktop or applications.

Cause: ZRAM (compressed swap) conflicting with 512MB dynamic VRAM allocation.

Solution: Disable ZRAM:

# Temporarily disable
sudo swapoff /dev/zram0

# Permanently disable
sudo systemctl disable systemd-zram-setup@zram0.service

# Or reduce ZRAM size
# Edit /etc/systemd/zram-generator.conf
[zram0]
zram-size = ram / 4  # Instead of ram / 2

Alternative: Switch from 512MB dynamic to fixed allocation (10GB RAM / 6GB VRAM) in BIOS.

4. Boot Timeout Issues

Diagnosis: System hangs for 90+ seconds then continues.

Possible causes: - Waiting for network timeout - systemd service failing - Missing swap partition

Solution: Check boot logs: 

# After successful boot
journalctl -b | grep -i "time"
journalctl -b | grep -i "fail"

# Look for timed out services
systemctl --failed

Disable problematic services: 

sudo systemctl disable <service-name>

Kernel Panic on Boot

Problem: Kernel Panic Error Message

Symptoms: - Boot process starts - Kernel panic message appears - Often mentions "unable to mount root" - System halts completely

Common Causes:

1. Wrong Kernel Version

Error messages: - "Kernel panic - not syncing: VFS: Unable to mount root fs" - "amdgpu initialization failed" - GPU-related crash messages

Solution: Boot older kernel:

  1. At GRUB menu, select "Advanced options"
  2. Choose older kernel (6.12 or 6.13)
  3. If system boots successfully, set as default:
# List all installed kernels
sudo grubby --info=ALL

# Set older kernel as default
sudo grubby --set-default /boot/vmlinuz-6.13.*

# Or remove broken kernel
sudo dnf remove kernel-6.15.5\* kernel-6.17.8\*  # Fedora (example versions)
sudo apt remove linux-image-6.15.5\* linux-image-6.17.8\*  # Debian/Ubuntu

2. Corrupted initramfs

Error messages: - "Failed to execute /init" - "Unable to find root device" - "No init found"

Solution: Regenerate initramfs:

  1. Boot from USB installer
  2. Chroot into installed system:
# Mount root partition
sudo mount /dev/nvme0n1p2 /mnt  # Adjust device name
sudo mount /dev/nvme0n1p1 /mnt/boot/efi  # If separate boot

# Chroot
sudo arch-chroot /mnt  # Arch-based
# Or on Debian/Ubuntu:
for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i; done
sudo chroot /mnt

# Regenerate initramfs
# Fedora/RHEL:
sudo dracut -f

# Debian/Ubuntu:
sudo update-initramfs -u -k all

# Arch:
sudo mkinitcpio -P

# Exit chroot and reboot
exit
sudo umount -R /mnt
sudo reboot

3. Missing Drivers in initramfs

Solution: Ensure amdgpu driver in initramfs:

# Fedora/RHEL - edit /etc/dracut.conf.d/amdgpu.conf
add_drivers+=" amdgpu "

# Debian/Ubuntu - edit /etc/initramfs-tools/modules
amdgpu

# Arch - edit /etc/mkinitcpio.conf
MODULES=(amdgpu)

# Regenerate initramfs (commands above)

GRUB/Bootloader Problems

GRUB Not Appearing

Symptoms: - System boots directly to black screen - No boot menu shown - Can't select options or edit entries

Solution:

Show GRUB Menu

Edit GRUB configuration to always show menu:

# Boot from live USB with nomodeset
# Mount system partition and chroot (see above)

sudo nano /etc/default/grub

# Find and change:
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=0

# To:
GRUB_TIMEOUT_STYLE=menu
GRUB_TIMEOUT=10

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

# Debian/Ubuntu:
sudo update-grub

# Arch:
sudo grub-mkconfig -o /boot/grub/grub.cfg

Force GRUB to Show

Temporary methods: - Hold Shift during boot (BIOS systems) - Tap Esc repeatedly during boot (UEFI systems) - Interrupt boot by power cycling during GRUB load

GRUB Command Line or Rescue Mode

Symptoms: - Boot drops to grub> prompt - Or grub rescue> prompt - No boot entries shown

Cause: GRUB can't find its configuration or boot files.

Solution from grub> prompt:

# List partitions
grub> ls
(hd0) (hd0,gpt1) (hd0,gpt2)

# Find root partition (try each)
grub> ls (hd0,gpt2)/boot
# If you see vmlinuz files, that's your boot partition

# Set root
grub> set root=(hd0,gpt2)
grub> set prefix=(hd0,gpt2)/boot/grub

# Load config
grub> insmod normal
grub> normal

Solution from grub rescue> prompt:

grub rescue> set prefix=(hd0,gpt2)/boot/grub
grub rescue> set root=(hd0,gpt2)
grub rescue> insmod normal
grub rescue> normal
grub rescue> boot

After successful boot, reinstall GRUB:

# Fedora:
sudo grub2-install /dev/nvme0n1
sudo grub2-mkconfig -o /boot/grub2/grub.cfg

# Debian/Ubuntu:
sudo grub-install /dev/nvme0n1
sudo update-grub

# Arch:
sudo grub-install --target=x86_64-efi --efi-directory=/boot/efi
sudo grub-mkconfig -o /boot/grub/grub.cfg

systemd-boot Issues

For distributions using systemd-boot instead of GRUB:

Problem: No boot entries or entries don't work.

Solution:

# Boot from live USB
sudo mount /dev/nvme0n1p2 /mnt
sudo mount /dev/nvme0n1p1 /mnt/boot

# Reinstall systemd-boot
bootctl --path=/mnt/boot install

# Regenerate entries
sudo arch-chroot /mnt  # Or appropriate chroot command
bootctl update
exit

# Reboot

Removing nomodeset After Driver Installation

Once drivers are installed, you MUST remove nomodeset for GPU acceleration to work.

Permanent Removal

Fedora/RHEL: 

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

# Find line:
GRUB_CMDLINE_LINUX_DEFAULT="quiet nomodeset"

# Remove 'nomodeset':
GRUB_CMDLINE_LINUX_DEFAULT="quiet"

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

# Reboot
sudo reboot

Debian/Ubuntu: 

sudo nano /etc/default/grub

# Remove 'nomodeset' from:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset"

# Update
sudo update-grub
sudo reboot

Arch: 

sudo nano /etc/default/grub

# Remove 'nomodeset'

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

systemd-boot: 

sudo nano /boot/loader/entries/arch.conf

# Remove 'nomodeset' from options line
options root=UUID=xxx rw nomodeset  # Before
options root=UUID=xxx rw            # After

# Save and reboot

Verify Removal

After reboot: 

# Check kernel command line
cat /proc/cmdline
# Should NOT contain 'nomodeset'

# Check GPU acceleration working
glxinfo | grep "direct rendering"
# Should show: "direct rendering: Yes"

# Check Vulkan
vulkaninfo --summary | grep deviceName
# Should show: AMD Radeon Graphics (RADV GFX1013)

BIOS Settings That Affect Boot

Certain BIOS settings can cause boot problems:

IOMMU (AMD-Vi)

Recommendation: MUST BE DISABLED (IOMMU is broken on BC-250)

Location: Advanced → AMD CBS → NBIO → IOMMU

Why disable: - IOMMU is broken on BC-250 - Causes display failures, black screens, and crashes - Does not work reliably even for virtualization/GPU passthrough

VRAM Allocation

Recommendation: 512MB (Dynamic) for most users

Location: Advanced → Chipset → UMA Frame Buffer Size

Important: - Settings don't stick without CMOS clear after flash - Fixed allocations (4GB, 6GB, 8GB) more stable for some use cases - Dynamic 512MB can conflict with ZRAM

Secure Boot

Recommendation: DISABLED

Why: - Custom kernels won't boot with Secure Boot - Patched kernels (frequency range mod) need it off - Most Linux distros work better with it disabled

CSM (Compatibility Support Module)

Recommendation: DISABLED (pure UEFI mode)

Why: - Modern Linux distros prefer UEFI - CSM can cause boot order issues - DisplayPort initialization better in UEFI mode

Hardware Power Issues

Board Powers On But Won't Boot

Symptoms: - Fan spins - LED lights up - No display, no boot activity - No BIOS access

Checks:

1. Verify 8-Pin Power Connected

  • Must be firmly seated
  • Check for bent pins
  • Ensure PSU rail providing 12V
  • Test with multimeter if possible

2. Minimum Power Requirements

  • 300W PSU minimum
  • 400W+ recommended for stability
  • Dell 220W bricks NOT sufficient under load
  • Use ATX PSU or server PSU (HP/Dell 750W+)

3. CMOS Battery

  • Try booting WITH battery installed
  • Some boards won't POST without CMOS battery
  • Use fresh CR2032

4. Short Circuit Check

  • Inspect board for metal debris
  • Check mounting standoffs not shorting traces
  • Look for bent capacitors touching heatsink

Diagnostic Commands

Check Boot Process

# View current boot
journalctl -b

# Previous boot (if current boot fails)
journalctl -b -1

# Kernel messages
dmesg | less

# Boot time analysis
systemd-analyze blame

# Critical errors only
journalctl -p 3 -b

Check GPU Initialization

# GPU detected?
lspci | grep VGA
# Should show: AMD/ATI Device [1002:13fe]

# Driver loaded?
lsmod | grep amdgpu

# GPU initialization errors
dmesg | grep -i amdgpu | grep -i error

# Firmware loading
dmesg | grep -i firmware

Check Display Connection

# Displays detected
xrandr --listproviders
# Should show: Provider 0: AMD Radeon Graphics

# DRM devices
ls -la /sys/class/drm/
# Should show card0, card0-DP-1

# Current display mode
xrandr

Check Kernel Command Line

# Current boot parameters
cat /proc/cmdline

# Should show parameters like:
# BOOT_IMAGE=/vmlinuz root=UUID=xxx rw quiet

# Should NOT contain 'nomodeset' after drivers installed

Recovery Procedures

Complete Boot Failure Recovery

If system completely fails to boot after changes:

Step 1: Boot Live USB - Use same distro as installed - Boot with nomodeset if needed

Step 2: Chroot Into System 

# Mount root partition
sudo mount /dev/nvme0n1p2 /mnt

# Mount boot if separate partition
sudo mount /dev/nvme0n1p1 /mnt/boot

# Mount system directories
for i in /dev /dev/pts /proc /sys /run; do
    sudo mount -B $i /mnt$i
done

# Chroot
sudo chroot /mnt

Step 3: Fix Configuration 

# Restore GRUB defaults
sudo nano /etc/default/grub
# Add nomodeset back temporarily

# Regenerate config
sudo grub2-mkconfig -o /boot/grub2/grub.cfg

# Or reinstall GRUB entirely
sudo grub2-install /dev/nvme0n1

Step 4: Install/Reinstall Drivers 

# Install Mesa 25.1+ (see distro guides)
# Regenerate initramfs
# Exit chroot and reboot

BIOS Recovery

If BIOS appears corrupted:

Method 1: Reflash via USB 1. Create bootable USB with BIOS files 2. Boot to USB (should happen automatically) 3. Wait for flash process (LED blinks) 4. Power off when complete 5. Clear CMOS 6. Boot and reconfigure

Method 2: Hardware Programmer If USB method fails:

  1. Get CH341A programmer (~$5 on AliExpress)
  2. Locate SPI flash chip on board (W25Q64)
  3. Use programmer to flash known-good BIOS
  4. See BIOS recovery guide for detailed steps

BIOS Recovery Guide →

Common Boot Issues Summary

Symptom Most Likely Cause Quick Fix
Black screen during install No drivers Add nomodeset
Black screen after install Drivers not installed Boot with nomodeset, install Mesa
Boots but no GRUB GRUB timeout 0 Hold Shift during boot
Kernel panic on boot Wrong kernel version Boot 6.12-6.14 kernel
Hangs at boot IOMMU enabled Disable IOMMU in BIOS
GRUB shows, then black Missing/wrong drivers Add nomodeset, install Mesa 25.1+
Works after BIOS flash, then fails CMOS not cleared Clear CMOS battery
Works, then breaks after update Kernel 6.15.0-6.15.6 or 6.17.8+ installed Install 6.15.7-6.17.7 or 6.12-6.14 LTS

Advanced: Boot with Custom Parameters

For testing or troubleshooting, add these parameters at GRUB:

# Basic display
nomodeset

# Disable AMD GPU completely (use CPU graphics)
modprobe.blacklist=amdgpu

# More verbose boot messages
quiet → remove this
loglevel=7

# Single user mode (root shell)
systemd.unit=rescue.target

# Emergency mode (minimal system)
systemd.unit=emergency.target

# Disable specific hardware
amdgpu.sg_display=0    # Scatter-gather display (pre-6.10)
iommu=off              # Disable IOMMU
acpi=off               # Disable ACPI (not recommended)

# Debug specific subsystem
amdgpu.debug=0xffff    # AMD GPU debug output
drm.debug=0x1f         # DRM debug output

FAQ

Q: I can access BIOS but OS won't boot at all. What do? A: Add nomodeset to kernel parameters at GRUB. This is the #1 solution for BC-250 boot issues.

Q: System worked yesterday, today won't boot. Nothing changed. A: Check if system updated kernel. Run uname -r from live USB after mounting system drive. If 6.15.0-6.15.6 or 6.17.8+, that's the problem.

Q: Installed drivers but still have black screen? A: Did you remove nomodeset after installing drivers? It must be removed from GRUB config.

Q: How do I know if my kernel is the problem? A: BC-250 works best with 6.15.7-6.17.7 or 6.12.x-6.14.x LTS. Kernels 6.15.0-6.15.6 and 6.17.8+ break GPU drivers. Avoid 6.10 and below (too old).

Q: BIOS seems dead after flashing. Bricked? A: 90% chance you just need to clear CMOS. Remove battery for 60 seconds. Almost never truly bricked.

Q: Can I prevent these boot issues? A: Yes! Avoid kernel 6.15.0-6.15.6 and 6.17.8+, keep Mesa 25.1+, disable IOMMU in BIOS, always clear CMOS after BIOS flash.

Related Guides: - Display Issues - Display-specific troubleshooting - Linux Installation - Distribution setup guides - BIOS Flashing - How to flash custom BIOS - Mesa Installation - Installing Mesa drivers - BIOS Recovery - Unbricking procedures