Apple Desktop Computer Bedienungsanleitung PDF herunterladen (Seite 64)

CHAPTER 5

Software

64 What Is Different

5. The Forth script transfers control to the Trampoline code, which functions as

the transition between Open Firmware and the beginning of the Mac OS

execution;

6. The Trampoline code decompresses the ToolBox ROM Image, gathers

information about the system from Open Firmware, creates data structures

based on this information, terminates Open Firmware, and rearranges the

contents of memory to an interim location in physical memory space;

7. The Trampoline code transfers control to the HardwareInit routine in the

ToolBox ROM Image;

8. The HardwareInit routine copies data structures to their correct places in

memory, and then calls the NanoKernel;

9. The NanoKernel ﬁlls in its data structures and then calls the 68K Emulator;

10. The 68K Emulator initializes itself, then transfers control to the startup

initialization code;

11. The startup initialization code begins execution, initializing data structures

and Managers, and booting the Mac OS.

All functions found in the old ToolBox ROM are present in the NewWorld boot

process, but occur at different times and places. To accomplish this, the code in

the ToolBox ROM Image and POST is simpliﬁed, while the Trampoline code

addresses the new functionality.

What Is Different 5

Even though ROM-in-RAM involves a fundamental change to the construction

of the product-speciﬁc part of the Mac OS, the changes in the code and its

execution are not that large. Many components are in changed locations, but

their functions with respect to boot time and run time have not greatly changed.

Many Mac OS components remain untouched.

Interrupt Handling 5

Interrupt handling is very different with the NewWorld approach. The

interrupt code has been rewritten to allow for dynamic creation of the interrupt

layout. The new code has two features that did not exist in the old code. One is

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Apple Desktop Computer Bedienungsanleitung Seite 64