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22 Constellation.2 SAS Product Manual, Rev. H
7.0 Physical/electrical specifications
This section provides information relating to the physical and electrical characteristics of the drive.
7.1 PowerChoice
TM
power management
Drives using the load/unload architecture provide programmable power management to tailor systems for per-
formance and greater energy efficiency.
The table below lists the supported PowerChoice modes. The further you go down in the table, the more power
savings you get. For example, Idle2 mode results in greater power savings than Idle1 mode. Standby mode
results in the greatest power savings.
PowerChoice modes
Mode Description
Idle_A Reduced electronics
Idle_B Heads unloaded. Disks spinning at full RPM
Idle_C Heads unloaded. Disks spinning at reduced RPM
Standby_Y Heads unloaded. Disks spinning at reduced RPM.
Recovery requires the NOTIFY (Enable Spinup) command.
Standby_Z Heads unloaded. Motor stopped (disks not spinning)
Recovery requires the NOTIFY (Enable Spinup) command.
PowerChoice
TM
can be invoked using one of these two methods:
• Power Condition mode page method—Enable and initialize the idle condition timers and/or the standby con-
dition timers. The timer values are based on the values set in the Power Condition mode page.
• START STOP UNIT command method—Use the START STOP UNIT command (OPERATION CODE 1Bh).
This allows the host to directly transition the drive to any supported PowerChoice mode.
If both the Power Condition mode page and START STOP UNIT command methods are used, the START
STOP UNIT command request takes precedence over the Power Condition mode page power control and may
disable the idle condition and standby condition timers. The REQUEST SENSE command reports the current
PowerChoice state if active and also the method by which the drive entered the PowerChoice state.
When the drive receives a command, all power condition timers are suspended if they were enabled via the
Power Condition mode page. Once all outstanding commands are processed, the power condition timers are
reinitialized to the values defined in the Power Condition mode page.