SEAGATE (ST8000VX004) - Инструкция по эксплуатации - Страница 11

Seagate SkyHawk  Serial ATA Product Manual, Rev. B

  10

2.5.4

Extended Power Conditions - PowerChoice

™

Utilizing the load/unload architecture a programmable power management inter face is provided to tailor systems 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 users go down in the table, the more power savings is actualized. For 
example, Idle_b results in greater power savings than the Idle_a power condition. Standby results in the greatest power savings. 

Each power condition has a set of current, saved and default settings. Default settings are not modifiable. Default and saved settings 
persist across power-on resets. The current settings do not persist across power-on resets. At the time of manufacture, the default, 
saved and current settings are in the Power Conditions log match.

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 Immediate and Idle Immediate also provide a

method to directly transition the drive into supported power conditions. 

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

S.M.A.R.T. Read Data Reports
• Attribute 192 - Emergency Retract Count
• Attribute 193 - Load/Unload Cycle Count

Power Condition Name

Power Condition ID

Description

Idle_a

81

H

Reduced electronics

Idle_b

82

H

Heads unloaded. Disks spinning at full RPM

Idle_c

83

H

Heads unloaded. Disks spinning at reduced RPM

Standby_z

00

H

Heads unloaded. Motor stopped (disks not spinning)