Technical information

CHAPTER 5
System Software
NewWorld Boot Process 83
Open Firmware Script 5
The bootinfo components normally do not need to be changed for each new
product. The Open Firmware script is automatically modified at build time to
have the correct offsets within the bootinfo file to the other two main
components.
Trampoline Code 5
The Trampoline code is the component of the NewWorld architecture that
handles the transition between Open Firmware and the Mac OS ROM Image. It
retrieves all necessary information about the system from Open Firmware,
instantiates RTAS, decompresses the Mac OS ROM Image, locates the Mac OS
NV-RAM partition, formats the system information into tables and data
structures for the Mac OS, terminates Open Firmware, moves information in
memory to safe locations, and transfers control to the Mac OS ROM Image.
Mac OS ROM Image 5
The NewWorld version of the Mac OS ROM Image is similar to the old Mac OS
ROM in that it has a similar layout and contains many of the same components
as it did before.
The Mac OS ROM Image includes code that contains hardware-specific support,
including ADB, VIA, Cuda/Egret, MESH SCSI, and the Heathrow/CHRP/
UltraDMA AIMs. In the future, that code can be moved out of the Mac OS ROM
Image when there is a mechanism to load it from a boot volume at boot time.
NewWorld Boot Process 5
Here is a high-level view of the execution path take when a NewWorld-based
computer boots.
1. The POST code runs (preliminary diagnostics, boot beep, initialization, and
setup), with possible intervention in the mini nub, a small debugging tool.
2. Open Firmware initializes and begins execution, including building the
device tree and the interrupt trees.