Whats a bootstrap partition?
(Please note: I’ve taken a few liberties with this explanation, and skipped over a few subtleties. This isn’t exactly what happens, but it should be close enough to satisfy most people. If you’d like more detailed technical information, you’re encouraged to search the various LinuxPPC lists for more information.) When your Mac first starts up, Open Firmware begins checking your partitions, beginning with the one pointed to by the environment variable “boot-device,” for a blessed folder (in the case of the MacOS, this folder is titled “System Folder,” but the name is irrelevant). It looks inside each blessed folder it finds for a file of type ‘tbxi.’ Upon finding this file, it checks to ensure that the file is a CHRP script, which is a set of instructions further directing Open Firmware on how to continue the start process. When you boot into the MacOS, the CHRP script loaded by OF is the MacOS ROM file, and this file in turn places a copy of the Mac OS ROM into memory. From there, the
