Mac OS X Internals: A Systems Approach

Apple initiated its transition from the 68K hardware platform to the PowerPC in 1994. Within the next two years, Apple's entire line of computers moved to the PowerPC. The various PowerPC-based Apple computer families available at any given time have often differed in system architecture,[1] the specific processor used, and the processor vendor. For example, before the G4 iBook was introduced in October 2003, Apple's then current systems included three generations of the PowerPC: the G3, the G4, and the G5. Whereas the G4 processor line is supplied by Motorola, the G3 and the G5 are from IBM. Table 31 lists the various PowerPC processors[2] used by Apple.

[1] System architecture refers to the type and interconnection of a system's hardware components, includingbut not limited tothe processor type.

[2] The list does not account for minor differences between processor modelsfor example, differences based solely on processor clock frequencies.

Table 31. Processors Used in PowerPC-Based Apple Systems

Processor

Introduced

Discontinued

PowerPC 601

March 1994

June 1996

PowerPC 603

April 1995

May 1996

PowerPC 603e

April 1996

August 1998

PowerPC 604

August 1995

April 1998

PowerPC 604e

August 1996

September 1998

PowerPC G3

November 1997

October 2003

PowerPC G4

October 1999

PowerPC G5

June 2003

PowerPC G5 (dual-core)

October 2005

On June 6, 2005, at the Worldwide Developers Conference in San Francisco, Apple announced its plans to base future models of Macintosh computers on Intel processors. The move was presented as a two-year transition: Apple stated that although x86-based Macintosh models would become available by mid-2006, all Apple computers would transition to the x86 platform only by the end of 2007. The transition was faster than expected, with the first x86 Macintosh computers appearing in January 2006. These systemsthe iMac and the MacBook Prowere based on the Intel Core Duo[3] dual-core processor line, which is built on 65 nm process technology.

[3] This processor was originally codenamed Yonah.

In this chapter, we will look at the system architecture of a specific type of Apple computer: a G5-based dual-processor Power Mac. Moreover, we will discuss a specific PowerPC processor used in these systems: the 970FX. We focus on a G5-based system because the 970FX is more advanced, more powerful, and more interesting in general than its predecessors. It is also the basis for the first 64-bit dual-core PowerPC processor: the 970MP.

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