In my tinkering with EFI I attempted to flash some backdoored firmware to a test MacBook that was kindly donated to science by a friend of mine. This resulted in the bastard doing the S.O.S. beeps and not booting, and it didn’t seem to be recoverable using the Firmware Restore CDs from Apple. I decided that since it was dead anyway I might as well try and recover it by re-flashing the firmware manually using the nifty Bus Pirate that I impulse-bought not long ago, and a copy of flashrom.
Thanks Russm! Via the contact form.