Hello,
I've switched my Acer C720 years ago to legacy boot mode (SeaBIOS) to be able to install another OS (FreeBSD). This required, after removing the write protection screw, the following commands:
Disable the software write protection.
# flashrom --wp-disable
Run set_gbb_flags.sh with no parameters.
# set_gbb_flags.sh GBB_FLAG_DEV_SCREEN_SHORT_DELAY 0x00000001 GBB_FLAG_FORCE_DEV_SWITCH_ON 0x00000008 GBB_FLAG_FORCE_DEV_BOOT_LEGACY 0x00000080 GBB_FLAG_DEFAULT_DEV_BOOT_LEGACY 0x00000400
Now set SeaBIOS as default.
# set_gbb_flags.sh 0x489
Enable back the software write protection.
# flashrom --wp-enable
This work fine and FreeBSD which I installed on a replaced SSD runs fine on the hardware. The original SSD still contains the ChromeOS.
Now I want to switch back to boot a few times ChromeOS from this SSD to see something in the boot messages of this and compare it with the sources. I doubt that the replace SSD will boot due to the changed gbb_flags and of course FreeBSD has no support for this tool. How I could change them back, for example, booting some Ubuntu version? Or is there any other standalone bootable tool to do so?
Thanks Matthias