User Manual

Constellation.2 SAS Product Manual, Rev. K 27

6.0 Physical/electrical specifications

This section provides information relating to the physical and electrical characteristics of the drive.

6.1 PowerChoice

power management

Drives using the load/unload architecture provide programmable power management to tailor systems for perfor-

mance and greater energy efficiency.

The table below lists the supported PowerChoice modes. The further you go down in the table, the more power sav-

ings you get. For example, Idle2 mode results in greater power savings than Idle1 mode. Standby mode results in the

greatest power savings.

PowerChoice modes

PowerChoice

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 condition

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.

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.