Zerocat’s Coreboot Machines  v0.10.0
How to create Zerocat’s Coreboot Machines like the ZC-X230 and others...
Build the Coreboot ROM Image (ThinkPad X60-32bit)

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This file lists essential steps for reference only and should be thoroughly reviewed. Please use the toolchain scripts instead. See Toolchain.


See Coreboot Build How-To:


$ git clone
$ cd coreboot
$ git checkout 4.8.1
$ git submodule update --init --checkout
$ make crossgcc-i386


$ make menuconfig

Use default values, but additionally select/deselect as specified:

  • Mainboard
    • Mainboard vendor (Lenovo) —>
    • Mainboard model (ThinkPad X60 / X60s / X60t) —>
    • ROM chip size (2048 KB (2 MB)) —>
    • (0x200000) Size of CBFS filesystem in ROM
  • General Setup
    • [*] Use CMOS for configuration values
  • Chipset
    • Include CPU microcode in CBFS (Do not include microcode updates) —>
  • Devices
    • Graphics initialization (Use native graphics init) —>
    • Display —>
      • Framebuffer mode (Linear "high-resolution" framebuffer) —>
  • Console
    • [ ] Serial port console output
  • Payload
    • Add a payload (An ELF executable payload) —>
    • "(payload.elf)" Payload path and filename

      File payload.elf should match your previously built executable GRUB payload file for platform i386-coreboot. See GRUB How-To.
    • Secondary Payloads —>
      • Select: Load coreinfo as a secondary payload
      • Select: Load nvramcui as a secondary payload
The .config file may contain your paths which you probably don't want to share with others.
We prefer to avoid CPU Microcode Updates on machines that are known to work well enough without (see libreboot’s documentation).
Otherwise select "Generate from tree".


When you have exit the menuconfig tool, type:

$ make

This will provide the coreboot.rom in folder build/.

Add Custom Files

Add Zerocat’s GRUB Configuration File

Use coreboot’s cbfstool to add the custom configuration file as etc/zerocat.cfg:

$ build/cbfstool build/coreboot.rom add -t raw -n etc/zerocat.cfg -f your/path/to/grub@2.02_zerocat.cfg
$ build/cbfstool build/coreboot.rom print

See grub@2.02_zerocat.cfg for reference. Before using it, please edit the file and adjust your keyboard layout which is currently pre-set via keymap.

Secondary Payloads

NVRAMCUI and Coreinfo

Secondary payloads nvramcui and coreinfo should be accompanied with an informative message about occasional freezes, what can be achieved with GRUB, but not with SeaBIOS. Therefor, let’s move them out of the SeaBIOS img/ search path:

$ for i in coreinfo nvramcui; \
  do \
    build/cbfstool build/coreboot.rom extract -m x86 -n img/$i -f $i.extracted \
      && build/cbfstool build/coreboot.rom remove -n img/$i \
      && build/cbfstool build/coreboot.rom add-payload -c lzma -n $i -f $i.extracted \
      && rm $i.extracted;
When invoking coreinfo fromout the GRUB Boot Menu, please get prepared for occasional freezes due to CPU exceptions and faults. See Coreinfo CPU Exceptions.
When invoking nvramcui fromout the GRUB Boot Menu, switch your RF Kill Switch off! Active bluetooth devices might freeze the application.
Hmm..., and secondary payloads nvramcui and coreinfo seem to freeze in case a fingerprint sensor is part of the system, so please unplug that sensor.

Add SeaBIOS Payload

Zerocat’s GRUB Configuration File already comes with a menu entry to chainload the SeaBIOS payload. Add files to the coreboot.rom as required:

$ build/cbfstool build/coreboot.rom add -t raw -n config-seabios -f your/path/to/seabios/.config
$ build/cbfstool build/coreboot.rom add -t raw -n vgaroms/vgabios.bin -f your/path/to/seabios/out/vgabios.bin
$ build/cbfstool build/coreboot.rom add-payload -n seabios.elf -f your/path/to/seabios/out/bios.bin.elf
$ build/cbfstool build/coreboot.rom print

Please read section “Adding SeaBIOS Payload” of the GRUB How-To for more information.

Add Background Images

Zerocat’s GRUB Configuration File has already been prepared to make use of background images, if available. Just add a first image like so:

$ build/cbfstool build/coreboot.rom add -t raw -n background.png -f your/path/to/background.png
$ build/cbfstool build/coreboot.rom print

See Zerocat’s background image for reference:

You may add up to three more images named background_1.png, background_2.png and background_3.png. This feature provides space for additional information, such as a documented flash procedure for example. Use hotkey 'i' in GRUB’s Boot Menu to cycle through the images.

Tweak Parameters in cmos.default

Tweak parameters gfx_uma_size, wwan and bluetooth in the ROM’s cmos.default file:

$ build/util/nvramtool/nvramtool -C build/coreboot.rom -w gfx_uma_size=64M
$ build/util/nvramtool/nvramtool -C build/coreboot.rom -w wwan=Disable
$ build/util/nvramtool/nvramtool -C build/coreboot.rom -w bluetooth=Disable

Inquire parameter’s possible values with option -e, i.e.:

$ build/util/nvramtool/nvramtool -C build/coreboot.rom -e gfx_uma_size

Our “standard” CMOS setup now looks like this:

$ build/util/nvramtool/nvramtool -C build/coreboot.rom -a
boot_option = Fallback
reboot_counter = 0x0
debug_level = Spew
nmi = Enable
gfx_uma_size = 64M
boot_devices = ''
boot_default = 0x40
cmos_defaults_loaded = Yes
lpt = Enable
hyper_threading = Enable
first_battery = Primary
bluetooth = Disable
wwan = Disable
wlan = Enable
trackpoint = Enable
sticky_fn = Disable
power_management_beeps = Enable
low_battery_beep = Enable
volume = 0x3
tft_brightness = 0xff
You will be able to modify these settings with the NVRAMCUI Payload upon boot time.


Your ROM should now be ready to go!

In order to reset old & obsolete CMOS settings, please remind to unplug the coin battery for some seconds after flashing.

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