Оригинальный сообщение: Dan ,
EFI is the systems BIOS chip which also has a small user settable EROM that stores the hardware PIN if a user decides to set it. In the newest version of EFI iCloud lock has been added. In addition some hardware info is stored which is not alterable. Given you have a MacBook Air you only have a removable SSD drive so there is no EFI involvement.