Manually Flashing Firmware

Caution

Flashing your own firmware has the potential to brick your device. Do not do this unless you are sure you know what you're doing and have a way to recover from a bad flash. Some level of knowledge with using the Linux command line is required.

USE THE SCRIPT

If the device still boots, it is not recommended to flash manually — not even a self-compiled image. Run the Firmware Utility Script and choose Flash Custom Firmware. Manual flashrom on a running machine is how people skip backups and lose VPD/HWID, or otherwise get in trouble.

This page is really just to document what the script does under the hood.

When to Flash Manually

Unbricking: the device will not boot, so the script cannot run. Use a SuzyQable, CH341A, or similar external programmer.

The in-OS procedure below is the same flow the script uses (write-protect, backup, preserve VPD/HWID/MRC, flashrom). Keep it as a reference; do not follow it as an install guide when the script is an option.

Prerequisites

Before proceeding with manual flashing:

Linux environment (native boot or live USB)
Firmware write-protect disabled (for full ROM flashing)
Battery charged (>20% for Chromebooks)
Backup of current firmware (critical!)
Recovery method available (SuzyQable, CH341A programmer, or another device to create recovery media)

Understanding Flashrom Options

Before running the commands, it's important to understand what the flashrom options do:

Common Options

-p internal: Use the internal SPI controller (flashing from the device itself)
-r <file>: Read firmware from flash chip to file
-w <file>: Write firmware from file to flash chip
-v <file>: Verify flash chip contents against file

Intel-Specific Options

--ifd: Use Intel Flash Descriptor layout
-i bios: Only read/write the BIOS region (SI_BIOS), not ME or descriptor regions

VERIFICATION OPTIONS

No flag (default): Verifies entire flash chip - slowest but safest
-N flag: Skips verification of regions not being written - faster, still safe for what was flashed
-n flag: Skips all verification - fastest but risky, only use if you can recover from a bad flash

For BIOS region-only flashing (-i bios), using -N is reasonable since it still verifies the written region. Avoid -n unless you have a recovery method available.

AMD-Specific Differences

AMD devices don't use Intel's IFD layout, so they don't need the --ifd or -i bios flags. The entire flash chip is written as a single region.

Platform-Specific Warnings

Ti50 Devices (generally 2023 and newer)

Devices with the Ti50 Google Security Chip (GSC) verify the AP's read-only firmware and the software WP registers at boot. Critical warnings:

Set AllowUnverifiedRo=always with gsctool (CCD must be Open) before you flash Full ROM or change software WP. Battery disconnect will not help.
If RO verification fails, the device will not boot — not even to Recovery Mode. A 15-minute key sequence can get you back; see Ti50 recovery.
If UEFI is already on the chip, ChromeOS gsctool is gone. Permanent disable is then SuzyQ console (ccd set AllowUnverifiedRo Always) or a CH341A if the image itself is bad.
Always create a backup before flashing

See Write Protection: Ti50 Considerations for detailed information.

Alderlake/Raptorlake Devices

Some newer devices may require additional steps or have specific quirks. Check the Known Issues page for device-specific information.

Manual Flashing Procedure

The steps below assume you are flashing an image named coreboot.rom; substitute the filename as necessary. This is the in-OS flow the Firmware Utility Script performs; for a brick, use the SuzyQable or CH341A guides instead.

Step 1: Download Required Tools

Download flashrom, cbfstool, and gbb_utility, then make them executable:

# Download and extract flashrom
wget -O flashrom.tar.gz https://mrchromebox.tech/files/util/flashrom_ups_libpci37_20240418.tar.gz
tar -zxf flashrom.tar.gz
chmod +x flashrom

# Download and extract cbfstool
wget https://mrchromebox.tech/files/util/cbfstool.tar.gz
tar -zxf cbfstool.tar.gz
chmod +x cbfstool

# Download and extract gbb_utility
wget https://mrchromebox.tech/files/util/gbb_utility.tar.gz
tar -zxf gbb_utility.tar.gz
chmod +x gbb_utility

Step 2: Backup Current Firmware

This step is critical! Always create a backup before flashing:

AMD devices:

sudo ./flashrom -p internal -r backup.rom

Intel devices:

sudo ./flashrom -p internal -r backup.rom --ifd -i bios

IMPORTANT

Verify the backup was created successfully and is non-zero size:

ls -lh backup.rom

Should show a file size of several megabytes (typically 8MB or 16MB).

Store the backup safely - copy it to USB drive or upload to cloud storage. This backup can save your device if something goes wrong.

Step 3: Extract and Preserve Critical Data

Your firmware contains device-specific data that must be preserved:

Extract VPD (Vital Product Data):

./cbfstool backup.rom read -r RO_VPD -f vpd.bin

Inject VPD into your custom ROM:

./cbfstool coreboot.rom write -r RO_VPD -f vpd.bin

Extract and inject HWID:

If your current firmware is from the Firmware Utility Script:

./cbfstool backup.rom extract -n hwid -f hwid.txt

If your current firmware is stock ChromeOS firmware:

./gbb_utility backup.rom --get --hwid > hwid.txt

Add HWID to your custom ROM:

./cbfstool coreboot.rom add -n hwid -f hwid.txt -t raw

NOTE

If the add command fails with "already exists", use remove first:

./cbfstool coreboot.rom remove -n hwid
./cbfstool coreboot.rom add -n hwid -f hwid.txt -t raw

Step 4: Flash Your Custom Firmware

Now flash the prepared firmware to your device:

AMD devices:

sudo ./flashrom -p internal -w coreboot.rom

Intel devices (with verification):

sudo ./flashrom -p internal --ifd -i bios -w coreboot.rom

Intel devices (skip verification of unwritten regions):

sudo ./flashrom -p internal --ifd -i bios -w coreboot.rom -N

Flashing typically takes 30-90 seconds on Intel devices (longer without -N), 60-120 seconds on AMD devices.

SUCCESS INDICATORS

Flashrom will display progress and verification messages. A successful flash ends with:

Reading old flash chip contents... done.
Erasing and writing flash chip... Erase/write done.
Verifying flash... VERIFIED.

Step 5: Verify the Flash (Optional but Recommended)

If you used the -n flag (skip all verification), or want to double-check, manually verify the flash:

Intel devices:

sudo ./flashrom -p internal --ifd -i bios -v coreboot.rom

AMD devices:

sudo ./flashrom -p internal -v coreboot.rom

NOTE

If you used -N (default for most Intel commands), the written region was already verified automatically. Manual verification is only necessary if you used -n or want extra assurance.

Step 6: Reboot

If flashrom reported success and verification passed, you're ready to reboot:

sudo reboot

FIRST BOOT

The first boot after flashing may take 30-90 seconds due to RAM training. Don't panic if you see a black screen - wait at least 90 seconds before assuming something went wrong.

Verifying Firmware Version After Flash

After successful boot, verify your firmware was flashed correctly:

From Linux terminal:

sudo dmidecode -t bios

From UEFI firmware setup menu:

Press ESC during boot
Check firmware version displayed on main screen

Additional Resources

Firmware Utility Script - The recommended method for most users
Unbricking Guide - Recovery from failed flash
Compiling Firmware - Build your own firmware from source
Flashrom Documentation - Official flashrom documentation
Write Protection - Understanding and disabling WP

External Flashing

If internal flashing fails or your device is bricked, you may need to flash externally using a hardware programmer. See the Unbricking Guide for detailed instructions on:

Using a CH341A programmer
Using a SuzyQable (CR50/Ti50 devices)
Proper flash chip clip placement and connection
External flashing procedures