User Manual

Constellation.2 Serial ATA Product Manual, Rev. G 19

2.8.4 Power-management modes

The drive provides programmable power management to provide greater energy efficiency. In most systems, you can

control power management through the system setup program. The drive features the following power-management

modes:

• Active mode

The drive is in Active mode during the read/write and seek operations.

• Idle mode

The buffer remains enabled, and the drive accepts all commands and returns to Active mode any time disc access

is necessary.

• Standby mode

The drive enters Standby mode when the host sends a Standby Immediate command. If the host has set the

standby timer, the drive can also enter Standby mode automatically after the drive has been inactive for a specifi-

able length of time. The standby timer delay is established using a Standby or Idle command. In Standby mode,

the drive buffer is enabled, the heads are parked and the spindle is at rest. The drive accepts all commands and

returns to Active mode any time disc access is necessary.

• Sleep mode

The drive enters Sleep mode after receiving a Sleep command from the host. In Sleep mode, the drive buffer is dis-

abled, the heads are parked and the spindle is at rest. The drive leaves Sleep mode after it receives a Hard Reset or

Soft Reset from the host. After receiving a reset, the drive exits Sleep mode and enters Standby mode with all cur-

rent translation parameters intact.

• Idle and Standby timers

Each time the drive performs an Active function (read, write or seek), the standby timer is reinitialized and begins

counting down from its specified delay times to zero. If the standby timer reaches zero before any drive activity is

required, the drive makes a transition to Standby mode. In both Idle and Standby mode, the drive accepts all com-

mands and returns to Active mode when disc access is necessary.

2.8.4.1 Extended Power Conditions - PowerChoice

Utilizing the load/unload architecture a programmable power management interface 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 you 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 con-

dition. Standby results in the greatest power savings.

Power modes Heads Spindle Buffer

Active Tracking Rotating Enabled

Idle_a ID Biased Rotating Enabled

Idle_b Parked Rotating Enabled

Idle_c Parked Rotating at lower RPM Enabled

Standby Parked Stopped Enabled

Sleep Parked Stopped Disabled