Apple Power Mac G5 - Manual (Page 6)

The World’s First 64-Bit
Desktop Processor
The Power Mac G5 marks the arrival of a 64-bit architecture to the personal computer
market. An all-new implementation of the PowerPC architecture, the G5 processor is
based on the execution core of IBM’s 64-bit POWER4 processor. Apple has teamed
with IBM to leverage this industry-leading design for the next generation of personal
computing.
The result? The revolutionary PowerPC G5, with clock speeds up to 2GHz, puts
enormous, seemingly infeasible tasks within easy reach. In addition to a highly parallel
execution core, it uses 64-bit data paths and registers to perform huge integer calcula-
tions and highly precise floating-point math in a single clock cycle—dramatically
accelerating audio, video, graphics, and scientific workflows.
An Exponential Leap in Computing Power
The label “32-bit” or “64-bit” characterizes the width of a microprocessor’s data stream,
which is a function of the sizes of its registers and the internal data paths that feed
the registers. A 64-bit processor moves data and instructions along 64-bit-wide data
paths, compared with the 32-bit-wide paths in 32-bit processors, such as the Pentium
4. In addition, 64-bit processors have wide registers that can store 64-bit numbers as
well as 32-bit numbers.
The leap from 32-bit to 64-bit processing represents an exponential advance in
computing power. With 32-bit registers, a processor has a dynamic range of 2
32 , or
4.3 billion—which means it can express integers from 0 to 4.3 billion. With 64-bit
registers, the dynamic range catapults to 2
64 , or 18 billion billion—4.3 billion times
larger than the range of a 32-bit processor. In addition, 64-bit processors enable
personal computers to address massive amounts of main memory. Since a memory
address is a special kind of integer and each address points to one byte in memory,
the 64-bit G5 processor can theoretically address 18 exabytes (18 billion billion bytes)
of virtual memory—or an amazing 4 terabytes of physical memory.
More practical and still unprecedented for a personal computer, the Power Mac G5
can be configured with 8GB of addressable memory
2 —four times more than what
is supported by a typical PC. Such large quantities of memory enable the system to
contain a complex 3D model, a scientific simulation, or a sequence of video entirely
in RAM—drastically reducing the time to access, modify, and render the data and
making it feasible to tackle gigantic projects on a desktop system.
6 Technology and
Performance Overview
Power Mac G5
4.3 billion times bigger
To grasp the exponential leap from 32-bit to
64-bit processing, imagine equating the range
of numbers a processor can express with a
two-dimensional area. A 32-bit processor can
express a range of integers equal to the size
of a postcard, while a 64-bit processor can
express a range of integers larger than the
island of Manhattan.
Postcard =
24 in. 2 (155 cm 2 )
Manhattan =
22 mi. 2 (57 km 2 )
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