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Western Digital Hard Disk Drive OEM Specification
9.4
Power Management Feature
The power management feature set allows an application client to modify the behavior of a device in a manner that
reduces the power required to operate. The power management feature set provides a set of commands and a timer
that enables a device to implement low power consumption modes.
The Power Management feature set implements the following set of functions.
1.
A Standby timer
2.
Idle command
3.
Idle Immediate command
4.
Sleep command
5.
Standby command
6.
Standby Immediate command
9.4.1
Power Mode
The lowest power consumption when the device is powered on occurs in Sleep Mode. When in sleep mode, the
device requires a reset to be activated.
In Idle Mode the device is capable of responding immediately to media access requests.
In Active Mode the device is under executing a command or accessing the disk media with read look -ahead function
or writes cache function.
9.4.1.1
Active Idle Mode
The electronics repeats on and off. And heads are track following and seeking, however the spindle is still rotated at
the full speed.
9.4.1.2
Low Power Idle Mode
Additional electronics are powered off, and heads are unloaded on the ramp, however the spindle is still rotated at
the full speed.
9.4.1.3
Low RPM Idle Mode
The heads are unloaded on the ramp, and the spindle is rotated at the 85-90% of the full speed.
9.4.1.4
Standby Mode
The device interface is capable of accepting commands, but as the media may not immediately accessible, there is a
delay while waiting for the spindle to reach operating speed.
