Abstract: A computer network is disclosed comprising a plurality of interconnected network devices including a plurality of client computers, an authentication server computer operated by a system administrator, and a disk drive connected to the authentication server computer. The disk drive comprises an interface for receiving the personal authentication data and user access data from the system administrator, a disk for storing data, and a disk controller for controlling access to the disk. An authenticator within the disk drive, responsive to the personal authentication data, enables the disk controller, and cryptographic circuitry encrypts the user access data received from the system administrator into encrypted data stored on the disk.

Abstract: A disk drive is disclosed comprising a disk having a plurality of tracks, a head actuated over the disk, and control circuitry for servicing an access command received from a host, wherein the access command identifies at least one of the tracks. The control circuitry identifies a band of tracks associated with the access command, maintains a counter for tracking an amount of time the head is within the band of tracks, and moves the head out of the band of tracks in response to the counter to facilitate wear prevention.

Abstract: The present invention may be regarded as a disk drive comprising a disk having a plurality tracks, each track comprising a plurality of data sectors. If an error occurs while attempting to read one of the data sectors, a retry operation is executed in an attempt to recover the errant data sector. Averaged read data is generated over multiple retry operations, and the averaged read data processed to recover the errant data sector. In one embodiment, the averaged read data comprises an averaged binary sequence detected over multiple retry operations. In another embodiment, the averaged read data comprises averaged read signal sample values generated over multiple retry operations.

Abstract: A disk drive is disclosed comprising a disk having a plurality of servo sectors forming a plurality of substantially linear servo wedges extending from an outer diameter of the disk to an inner diameter of the disk, wherein each servo sector is written using perpendicular magnetic recording. The disk drive further comprises a head coupled to a distal end of an actuator arm that is rotated by a rotary actuator about a pivot in order to actuate the head radially over the disk in a substantially arcuate path.

Abstract: A method and apparatus is disclosed for adjusting at least one of a supply voltage and a clocking frequency applied to digital circuitry of a computing device, wherein the digital circuitry comprises a critical path circuit. A propagation delay frequency representing a propagation delay of the critical path circuit is generated, and a frequency error signal is generated representing a difference between a reference frequency and the propagation delay frequency. At least one of the supply voltage and the clocking frequency is adjusted in response to the frequency error signal.

Abstract: A disk drive is disclosed comprising a disk and a voice coil motor (VCM) having a voice coil for actuating a head over the disk. A VCM driver comprises an H-bridge driver having a plurality of driver switches for driving current through the voice coil to ground. A first pulse width modulated (PWM) signal controls a first voltage level driving the voice coil relative to a duty cycle of the first PWM signal, and a second PWM signal controls a second voltage level driving the voice coil relative to a duty cycle of the second PWM signal, wherein the first voltage level is greater than the second voltage level.

Abstract: A disk drive is disclosed comprising a disk, a head actuated over a surface of the disk, and a spindle motor for rotating the disk. The spindle motor comprises a ring-shaped stator having a plurality of stator teeth each wound with a winding. The spindle motor further comprises a hub having a plurality of magnets for interacting with the stator teeth to rotate the hub about the shaft when the windings are energized. A ring-shaped shield is disposed in a vertical gap between the windings and the hub to reduce a voltage coupled from the windings to the surface of the disk.

Abstract: A disk drive is disclosed which executes a rotational position optimization (RPO) algorithm for selecting a next command to execute out of a plurality of pending commands. The RPO algorithm comprises a first phase and a second phase. The first phase of the RPO algorithm is executed relative to a first priority and in response to at least one non-real-time parameter. The second phase of the RPO algorithm is executed relative to a second priority higher than the first priority and in response to at least one real-time parameter.

Abstract: A disk drive is disclosed comprising a disk surface having a plurality of concentric, radially spaced tracks, wherein each track comprises a plurality of data sectors and a plurality of servo sectors. At least two different index marks are distributed around the circumference of the disk surface. A servo sector counter is initialized relative to which index mark is detected, wherein the servo sector counter identifies a circumferential location of the servo sectors.

Abstract: A disk drive is disclosed comprising a microprocessor and a power driver for generating at least one actuator signal applied to the VCM actuator, wherein a serial communication circuit is used to communicate with the power driver. At least one control component periodically generates a control signal, wherein the control signal is transmitted at a substantially constant periodic interval using the serial communication circuit, and a timer times the periodic interval. A job queue controller queues and arbitrates serial communication requests to access the power driver using the serial communication circuit. The serial communication requests include a request to transmit the control signal and requests generated by the microprocessor. The job queue controller services a communication request generated by the microprocessor if the communication request can be serviced before the timer expires.

Abstract: A disk drive is disclosed for optimizing write current settings relative to drive operating characteristics and an ambient temperature reading. Test data is written to and read from the disk using different write current settings to generate a plurality of corresponding quality metrics. The quality metrics are evaluated to generate an optimized write current setting for the ambient temperature reading. In one embodiment, the first write current setting is selected relative to a previously optimized write current setting that corresponds to the ambient temperature reading. This embodiment expedites the optimization process by testing write current settings surrounding a previous write current setting rather than testing the entire range of write current settings.

Abstract: A disk drive is disclosed which demagnetizes the head after a write operation. Write circuitry applies a write signal to the head in order to write data to a selected data sector during a write operation, wherein the write signal comprises a predetermined write current amplitude. Control circuitry demagnetizes the head at the end of the write operation by maintaining the write current amplitude while increasing a frequency of an AC write signal applied to the head over a predetermined demagnetization interval, wherein increasing the frequency of the AC write signal decreases an amplitude of the AC write signal when observed at the head.

Abstract: A disk drive is disclosed comprising a disk having a plurality of tracks, and a head actuated over the disk. Control circuitry heats the head in order to reduce a fly-height of the head, and computes a target servo sector to begin a preheat period. The control circuitry decreases the heat so that the fly-height is increased during at least part of a seek operation to seek the head from a first track to a second track. When the head reaches the target servo sector, the control circuitry increases the heat to decrease the fly-height during the preheat period.

Abstract: A disk drive is disclosed comprising control circuitry for generating a control signal applied to a VCM in response to a position error signal (PES) generated from reading embedded servo sectors and a feed-forward compensation value that compensates for a repeatable runout (RRO) disturbance. The feed-forward compensation value is generated for each servo sector in response to an RRO estimate ? computed recursively for each servo sector according to: S ^ n + 1 = S ^ n - ? ? [ S ^ n - 1 n ? ? i = 1 n ? ? PES i ] wherein: ? is a predetermined fraction; PESi is the position error signal generated for a selected servo sector during an ith revolution of the disk; and n represents a number of disk revolutions.

Abstract: A disk drive is disclosed comprising a disk having a plurality of tracks, an actuator arm, a head connected to a distal end of the actuator arm, and a voice coil motor (VCM) for rotating the actuator arm about a pivot to actuate the head over the disk. A driving current is applied to the VCM to control the motion of the actuator arm. A back EMF voltage generated by the VCM is detected, and a velocity of the VCM is estimated in response to the back EMF voltage. The estimated VCM velocity is compared to a target velocity in a velocity profile, wherein the velocity profile comprises at least an acceleration component and a coast component. The driving current is adjusted in response to the comparison so that the velocity of the VCM substantially follows the velocity profile.

Abstract: A disk drive is disclosed comprising a disk having a plurality of servo bursts written using perpendicular magnetic recording, wherein each servo burst is written at a servo burst frequency. A fill pattern is written between the servo bursts using perpendicular magnetic recording at a frequency substantially equal to an even harmonic of the servo burst frequency, and a phase shift occurs at the transition between the servo burst and the fill pattern. A head is actuated over the disk, and a sampling device samples a read signal emanating from the head to generate a sequence of read signal sample values. Control circuitry demodulates the servo bursts from the sequence of read signal sample values by computing a single-point Discrete Fourier Transform (DFT) at the servo burst frequency.

Abstract: A method and apparatus is disclosed for writing product servo sectors to a disk of a disk drive to define a plurality of data tracks. The disk drive comprises the disk and a head actuated over the disk. The disk comprises a plurality of spiral tracks which are read using the head to synchronize a write clock and to generate a position error signal (PES) according to a PES algorithm used to maintain the head along a first servo track while writing product servo sectors along the first servo track. The PES algorithm is adjusted to seek the head to a second servo track, and the head is used to write product servo sectors along the second servo track.

Abstract: A disk drive and method for estimating a sinusoidal error in a wedge time period is disclosed. An estimated WTP is calculated according to: EST_WTP=RTP+â*cos(2?k/N)+{circumflex over (b)}*sin(2?k/N) wherein RTP is a reference time period corresponding to a nominal WTP, k is an index representing a servo wedge, and {â,{circumflex over (b)}} are adjustable coefficients. A wedge time error e(k) is estimated as the difference between the estimated WTP and a detected actual WTP. The coefficients {â,{circumflex over (b)}} for generating the estimated WTP are adjusted according to: â(k+1)=â(k)?G*e(k)*cos(2?k/N) {circumflex over (b)}(k+1)={circumflex over (b)}(k)?G*e(k)*sin(2?k/N) wherein G is a predetermined gain.

Abstract: A disk drive is disclosed for executing a program comprising a plurality of instructions. The disk drive comprises a primary memory for storing the instructions, and a cache memory for caching the instructions. The cache management is enhanced by not re-filling the cache due to accessing a non-sequential immediate operand.

Abstract: A disk drive is disclosed comprising a disk and a head actuated over the disk. The head comprising a first head terminal and a second head terminal. The disk drive further comprises an electrostatic discharge (ESD) protection circuit comprising a first depletion mode metal oxide semiconductor field effect transistor (MOSFET) comprising a gate terminal and a first and second transistor terminals. The first transistor terminal of the first depletion mode MOSFET is coupled to the first head terminal, and the second transistor terminal of the first depletion mode MOSFET is coupled to the second head terminal. The gate terminal is biased to turn on the first depletion mode MOSFET while the disk drive is powered down, thereby shorting the first and second head terminals to protect the head from ESD.