After successfully flashing three Supermicro X9SCD motherboards (BIOS version x9scd8.612) using my standard FreeDOS ISO and the command:

AFUDOSU.EXE x9scd8.612 /P /B /N /K /R

All systems exhibited the same post-flash behavior: normal OS functionality but complete inability to enter BIOS setup, displaying only error code "AB" on the screen. This occurred despite:

• Using a proven flash methodology
• Successful OS installation (Windows Server 2019)
• Existing Linux boots working normally

The issue appears potentially related to the BMC/IPMI subsystem, evidenced by:

1. Java security exceptions appearing with IPMI firmware 3.50
2. Different behavior between 3.50 and 3.54 firmware versions
3. Persistent BIOS entry failure even on untouched systems

Here's my troubleshooting methodology so far:

1. Verified flash completion status (all reported success)
2. Attempted CMOS reset via jumper and battery removal
3. Tried alternate keyboard connections (PS/2 vs USB)
4. Tested different video output methods (IPMI KVM vs physical ports)

While investigating the root cause, these approaches yielded partial success:

// Forced BIOS recovery method
1. Create bootable FreeDOS USB with AFUDOSU.EXE and BIOS file
2. Use modified flash command:
AFUDOSU.EXE x9scd8.612 /P /B /N /K /R /X /C
3. Power cycle with CMOS jumper cleared

The IPMI subsystem may require these additional steps:

# IPMI firmware update command example
./SUM -i 192.168.1.100 -u admin -p admin -c UpdateBMC --file BMC_3.54.bin

# BMC factory reset procedure
ipmitool -H 192.168.1.100 -U admin -P admin mc reset cold

These X9SCD-specific factors should be noted:

• MicroCloud chassis may affect thermal thresholds
• Dual BIOS chips require special handling
• Certain PCIe configurations can interfere with POST

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After successfully flashing three Supermicro X9SCD motherboards with BIOS version x9scd8.612 using my standard FreeDOS ISO and AFUDOSU.EXE utility:

AFUDOSU.EXE x9scd8.612 /P /B /N /K /R

All systems exhibited the same post-flash behavior: while fully functional for OS operations (Windows Server 2019 installation and Linux boot confirmed), BIOS access became impossible. The systems consistently displayed an "AB" error code during BIOS entry attempts.

Key findings during initial troubleshooting:

• IPMI firmware version correlation: Systems running 3.50 showed Java KVM security exceptions while 3.54 worked normally
• BIOS flashing completed without errors across all systems
• The issue appeared even on an untouched X9SCD system running IPMI 3.54

Several approaches were tested for recovery:

# Force BIOS recovery via IPMI
ipmitool -I lanplus -H [BMC_IP] -U [USER] -P [PASS] raw 0x30 0x70 0x01 0x01

# Alternative flash method with different switches
AFUDOSU.EXE x9scd8.612 /P /B /K /R /X

None of these methods resolved the BIOS access issue, though the systems remained operational.

The Java KVM security exception pattern suggested potential BMC-related issues. Testing revealed:

• BMC reset commands via IPMI had no effect
• Full power cycle (AC disconnect) didn't restore BIOS access
• Different KVM clients (iKVM, HTML5) showed identical behavior

The working solution involved:

1. Physical jumper reset (JP1 clear CMOS)
2. Secondary flash using alternative utility:

# Using AMI Firmware Update Utility instead
AFUWINx64.EXE /O x9scd8.612 /P /B /N /K

Key differences in the successful approach:

• Performed from Windows environment instead of FreeDOS
• Used different flash utility variant
• Applied after complete power discharge (10+ minutes)

For future X9SCD BIOS operations:

# Recommended flash command sequence
AFUDOSU.EXE x9scd8.612 /P /B /N /K /C /R

# Mandatory post-flash steps
1. Clear CMOS via jumper
2. Full power cycle (AC disconnect for >5 minutes)
3. Initial BIOS setup via serial console if available

The most likely scenario involves:

• NVRAM corruption during flash process
• Interaction between IPMI firmware and BIOS handshake
• Potential timing issue in POST sequence