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increase with increasing advanced power management levels. The advanced power management levels contain
discrete bands, described in the section of Set Feature command in detail.
This feature set uses the following functions:
• A SET FEATURES subcommand to enable Advanced Power Management
• A SET FEATURES subcommand to disable Advanced Power Management
The Advanced Power Management feature is independent of the Standby timer setting. If both Advanced Power
Management level and the Standby timer are set, the device will go to the Standby state when the timer times out or
the device's Advanced Power Management algorithm indicates that it is time to enter the Standby state.
The IDENTIFY DEVICE response word 83, bit 3 indicates that Advanced Power Management feature is supported
if set. Word 91, bit 7-0 indicates that Advanced Power Management is enabled if set. Word 91, bits 7-0 contain the
current Advanced Power Management level if Advanced Power Management is enabled.
11.7.1 Performance Idle Mode
This mode is usually entered immediately after Active mode command processing is complete, instead of
conventional idle mode. In Performance Idle mode, all electronic components remain powered and full frequency
servo remains operational. This provides instantaneous response to the next command. The duration of this mode is
intelligently managed as described below.
11.7.2 Active Idle Mode
In this mode, power consumption is 45–55% less than that of Performance Idle mode. Additional electronics are
powered off and the head is parked near the mid-diameter of the disk without servoing. Recovery time to Active
mode is about 20 ms.
11.7.3 Low Power Idle Mode
Power consumption is 60–65% less than that of Performance Idle mode. The heads are unloaded on the ramp but
the spindle is still rotated at the full speed. Recovery time to Active mode is about 300ms.
11.7.4 Transition time
The transition time is dynamically managed by the user's recent access pattern, instead of fixed times. The ABLE-3
algorithm monitors the interval between commands instead of the command frequency of ABLE-2. The algorithm
supposes that the next command will come with the same command interval distribution as the previous access
pattern. The algorithm calculates the expected average saving energy and response delay for next command in
several transition time case based on this assumption. And it selects the most effective transition time with the
condition that the calculated response delay is shorter than the value calculated from the specified level by Set
Feature Enable Advanced Power Management command.
The optimal time to enter Active Idle mode is variable depending on the recent behavior of the user. It is not possible
to achieve the same level of Power savings with a fixed entry time into Active Idle because every user's data and
access pattern is different. The optimum entry time changes over time.
The same algorithm works for entering into Low Power Idle mode and Standby mode, which consumes less power
but needs more recovery time switching from this mode to Active mode.
Travelstar 80GN Hard Disk Drive Specification
76
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