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TUTORIALS / HARDWARE

CUSTOM BIOS FLASHING

DIFFICULTY: INTERMEDIATE UPDATED: 1 WEEK AGO

⚠️ BRICK RISK WARNING

Flashing incorrect BIOS can permanently damage your motherboard. Always have a backup BIOS chip or dual-BIOS motherboard.

INTRODUCTION

Most motherboards ship with locked or limited BIOS/UEFI options. Custom BIOS mods unlock advanced settings like undervolting limits, memory timing controls, and hidden menus not available to average users.

PREREQUISITES

  • CH341A Programmer - $5-10 on AliExpress for external flashing
  • SOIC8 Clip - To connect to BIOS chip without desoldering
  • UEFITool - For extracting and modifying UEFI modules
  • HxD Hex Editor - For binary modifications
BIOS Menu with Unlocked Settings

STEP-BY-STEP GUIDE

Step 1: Download Stock BIOS

Get your motherboard's official BIOS from the manufacturer's website. This is your backup and base for modifications.

Step 2: Extract the BIOS Image

# Open UEFITool
File → Open → Select your BIOS file

# Extract the Setup module
Search for "Setup" → Right-click → Extract Body
Save as setup_original.bin

Step 3: Modify BIOS Settings

Use IFR Extractor to list all available options:

ifrextract setup_original.bin setup.txt

Find hidden variables (e.g., CFG Lock, Overclocking Lock) and note their offsets.

Edit with HxD to change values from 01 (Enabled/Locked) to 00 (Disabled/Unlocked).

Step 4: Rebuild BIOS Image

Use UEFITool to replace the original Setup module with your modified one, then save the new complete BIOS image.

Step 5: Flash via CH341A (Safest Method)

  1. Power off PC completely and unplug PSU
  2. Locate the BIOS chip on motherboard (usually 8-pin SOIC near 24-pin power)
  3. Attach SOIC8 clip to chip, connect to CH341A programmer
  4. Use AsProgrammer software to read current BIOS (verify byte-for-byte match with stock)
  5. Write your modified BIOS
  6. Verify write was successful
  7. Remove clip and power on

COMMON MODIFICATIONS

  • CFG Lock Disable: Allows undervolting on Intel CPUs
  • Advanced Memory Timings: Access to sub-timings for extreme overclocking
  • Custom Boot Logos: Replace OEM logo with custom image
  • TDP/PL Limits: Remove power limit restrictions