3.8.4.1Extended Power Conditions - PowerChoiceTM
Utilizing the load/unload architecture a programmable power management interface is provided to tailor sys- tems for reduced power consumption and performance requirements.
The table below lists the supported power conditions available in PowerChoice. Power conditions are ordered from highest power consumption (and shortest recovery time) to lowest power consumption (and longest recovery time) as follows: Idle_a power >= Idle_b power >= Idle_c power >= Standby_z power. The further you go down in the table, the more power savings is actualized. For example, Idle_b results in greater power sav- ings than the Idle_a power condition. Standby results in the greatest power savings.
Power Condition Name | Power Condition ID | Description |
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|
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Idle_a | 81H | Reduced electronics |
Idle_b | 82H | Heads unloaded. Disks spinning at full RPM |
Idle_c | 83H | Heads unloaded. Disks spinning at reduced RPM |
Standby_z | 00H | Heads unloaded. Motor stopped (disks not spinning) |
Each power condition has a set of current, saved and default settings. Default settings are not modifiable. Default and saved settings persist across
PowerChoice is invoked using one of two methods
•Automatic power transitions which are triggered by expiration of individual power condition timers. These timer values may be customized and enabled using the Extended Power Conditions (EPC) feature set using the standardized Set Features command interface.
•Immediate host commanded power transitions may be initiated using an EPC Set Features "Go to Power Condition" subcommand to enter any supported power condition. Legacy power commands Standby Imme- diate and Idle Immediate also provide a method to directly transition the drive into supported power condi- tions.
PowerChoice exits power saving states under the following conditions
•Any command which requires the drive to enter the PM0: Active state (media access)
•Power on reset
PowerChoice provides the following reporting methods for tracking purposes
Check Power Mode Command
• Reports the current power state of the drive
Identify Device Command
•EPC Feature set supported flag
•EPC Feature enabled flag is set if at least one Idle power condition timer is enabled
Power Condition Log reports the following for each power condition
•Nominal recovery time from the power condition to active
•If the power condition is Supported, Changeable, and Savable
•Default enabled state, and timer value
•Saved enabled state, and timer value
•Current enabled state, and timer value
Constellation ES Serial ATA Product Manual, Rev. D | 15 |