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Asset management software that reports the kind of computer it is running on can obtain the value of the
model property from the IOService plane of the IORegistry. For the PowerBook G4 17-inch computer, the
value of the model property is PowerBook5,1.
Power Saving Features
The PowerBook G4 17-inch computer has several profiles to save power. These profiles are labeled on the
Energy Saver panel of System Preferences.
Reduced Processor Performance
The PowerBook G4 17-inch computer reduces both processor speed and voltage to save power. Reduced
processor speed allows the software to change the processor’sclock speed, slowing downto conserve power
or speeding up when more speed is needed. The slower clock speed is 667 MHz and the L3 cache is turned
off.
The user interface for the reduced processor speed is located in the options tab under the Energy Saver panel
in System Preferences.
Operating Modes
The power management protocols on thePowerBook G4 17-inch computer support twopower-saving modes:
idle and sleep.
● Idle: The system is idling with the main processor stopped in a halted, low-power state. All clocks are
running; the system canreturn torunning code within a few nanoseconds. Cache coherency is maintained
in this state.
● Sleep: The system is completely shut down, with only the DRAM state preserved for quick recovery. All
processors are powered off with their state preserved in DRAM. All clocks in the system are suspended
except for the 32.768 kHz timebase crystal on the PMU99 IC.
The computer automatically enters idle mode after several seconds of inactivity. If the computer is attached
to a network, it is able to respond to service requests and other events directed to the computer while it is
in idle mode.
While it is connected to an AC power supply, the computer can also respond to network activity when it is
in sleep mode. The user can enable this feature by selecting Wake-on-LAN in the Energy Saver panel of
System Preferences.
When operating on the battery in sleep mode, the computer consumes less than 1 watt of power, meeting
the Energy Star power-saving standard. When operating on the power adapter in sleep mode, the combined
computer and adapter consume 3 to 4 watts of power.
Important: Peripherals such as PCMCIA cards and USB devices that do not conform to the computer’spower
management protocols prevent the computer from switchingto sleepmode and so deny the user the benefits
of this energy-saving mode. When such peripherals are attached to the computer, the operating system
displays a dialog to inform the user that the computer no longer meets the Energy Star requirements.
System Software 15
Legacy Document | 2003-03-01 | © 2003 Apple Computer, Inc. All Rights Reserved.
CHAPTER 1
Overview of PowerBook G4 17-inch