Specifications

CHAPTER 4
Software
38 ROM Software
The first part of this chapter describes the software in the Macintosh LC 520 computer’s
ROM. The second part describes the system software that supports the new features of
the Macintosh LC 520 computer.
ROM Software 4
The ROM in the Macintosh LC 520 computer is based on the ROM for the
Macintosh LC III with the necessary changes to support machine-specific hardware.
Unchanged Functions 4
Many ROM software components in the Macintosh LC 520 computer are functionally the
same as their counterparts in the Macintosh LC III. Those components are
■ the Slot Manager
■ network booting routines
■ Color QuickDraw
■ floating-point arithmetic routines
■ SANE routines
The AppleTalk routines are no longer in the ROM; they are now in the system software,
but they are similar to their counterparts in the ROM in the Macintosh LC III.
MMU Initialization 4
The code has been modified to support the memory addressing used by the
Macintosh LC 520 computer. There are new MMU tables to match the address mapping.
Machine Identification 4
The ROM includes new tables and code for identifying the machine.
Applications can find out which computer they are running on by using the Gestalt
Manager routines; see Inside Macintosh, Volume VI. The 'gestaltMachineType' value
for the Macintosh LC 520 computer is 56 (hexadecimal $38).
RAM Sizing and Addressing 4
The Macintosh LC 520 computer uses the same code as the Macintosh LC III for
determining the size of RAM, for setting up the MMU to make the RAM addresses
contiguous, and for address decoding.
To be able to run with virtual memory active, the Macintosh LC 520 computer uses the
32-bit Memory Manager and runs in 32-bit mode.