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Macintosh System Evolution

For their the second generation, Power Macintosh computers are switching from NuBus to the more standard PCI bus. This change means that many useful new PCI-based peripheral devices will become available for Macintosh computers.

To provide improved I/O support in Mac OS, Apple is introducing a native I/O framework that includes a set of driver services and mechanisms separate from those available to previous Macintosh device drivers. The native I/O framework includes these new features:

• native PowerPC execution of all driver code
• support modern types such as PCI bus and Card Bus
• new Device Manager support for concurrent operations
• improved interrupt mechanisms
• driver support services
• a Name Registry

Mac OS provides these features only for native device drivers. Existing drivers written in code for MC68000-family microprocessors (called 68K drivers) will continue to work as they have in the past, but inclusion of the new I/O framework marks the beginning of the transition of all Mac OS drivers to the native model described in this chapter. The model standardizes Mac OS driver design so that PCI and non-PCI device drivers can be written to a single specification.