The invention may be embodied in a method for operating a disk drive in a mobile
device to optimize power usage. The mobile device may be a hand held computing
device such as a personal digital assistant (PDA) or a mobile terminal such as
a cellular telephone. Immediately after responding to a disk access command, the
disk drive is in first operating mode that consumes a relatively high level of
power and may transition to a second operating mode that consumes a relatively
low level of power. A transition from the second operating mode to the first operating
mode consumes a transition quantity of power. A predictive technique tracks a user's
usage pattern and adapts an operating mode transition time based on the usage pattern.
