Abstract: A disk drive employs a method of operating a spindle motor to respond to a spin-down command to reduce the time required for spinning down and subsequently spinning up the spindle motor. The disk drive is connectable to a power supply having a fixed DC voltage. The spindle motor includes a stator having a plurality of windings and a rotor rotatable at a variable spin-rate. The rotor has an angular position relative to the stator. The disk drive includes switching elements coupled to the fixed DC voltage and the plurality of windings. The switching elements are controlled to sequentially apply the fixed DC voltage across a selected combination of the windings to generate a negative torque on the rotor such that a controlled braking operation is performed to decelerate the rotor to a selected spin-rate .omega.1. After the variable spin-rate is reduced to the selected spin-rate .omega.

Abstract: A method of mapping sequential logical data blocks to multiple disk surfaces. Data blocks are written to a predetermined number of adjacent tracks on each surface before performing a head switch to write data on another surface. The predetermined number of tracks are written on each surface in turn before performing a seek and head switch to continue writing on another predetermined number of tracks on each surface. After each head switch to continue writing from the radial position reached when writing the previous group of tracks, the direction of track incrementing or decrementing reverses so that the actuator moves back and forth in a "serpentine" manner.

Abstract: A method of centering a disk pack on a base rotatably supporting the disk pack includes performing a series a steps while the disk pack is rotating. A reference timing signal is generated. A first imbalance in the rotating disk pack is detected, and a first imbalance signal is produced. The first imbalance signal is correlated with the reference timing signal to produce a first correlation value, which indicates a location of the first imbalance relative to the reference timing signal. Based upon the first correlation value, a first impact is applied to the base, causing the base to shift relative to the disk pack. As a result of the first impact, the first imbalance moves to a second imbalance. The second imbalance is detected, and a second imbalance signal is produced. The second imbalance signal is correlated with the reference timing signal to produce a second correlation value, which indicates a location of the second imbalance relative to the reference timing signal.

Abstract: A method for reducing data access time in a disk drive. The disk drive includes an actuator and a servo controller. The servo controller commands the actuator to perform a seek from a current position to a target position using a profile of command effort to the actuator. The profile comprises an acceleration profile and a deceleration profile. In one aspect, the method includes defining a read profile for a seek used to position the actuator to execute a read command. A write profile is defined for a seek used to position the actuator to execute a write command, the write profile being different from the read profile for a respective seek distance. The read and write seeks are performed using the read profile and the write profile. The average time required for performing a seek command is reduced as a result of the difference between the read profiles and the write profiles.

Abstract: A disk drive is connectable to a power supply having a fixed DC voltage. The disk drive includes a voice coil motor (VCM) and a spindle motor having a plurality of windings and a rotor rotatable at a variable spin-rate. A spindle motor driver is coupled to the fixed DC voltage and at least one of the windings for controlling the spin-rate of the rotor. The rotor has permanent magnets that induce an AC voltage across the windings while the rotor is rotating. A rectifier circuit rectifies the AC voltage across at least one of the windings to produce a rectified DC voltage. A first switch provides the rectified DC voltage to a first node. A second switch provides the fixed DC voltage to the first node. The first node has a first node DC voltage that is determined by the rectified DC voltage provided by the first switch and the fixed DC voltage provided by the second switch. The first node DC voltage is greater than the fixed DC voltage during a track seeking operation in the disk drive.

Abstract: The disk drive provides a method of adaptively managing a cache segment divided into chunks by defining an unavailable data type to be stored in an element of a chunk array which indicates that the chunk is not available, and defining an available data type to be stored in an element of the chunk array that indicates the chunk is available and that indicates the number of consecutive chunks that are available. The disk drive also computes a number of chunks needed to fit the request length and scans the chunk array to find a first available element whose available data type meets a predetermined criteria for the number of chunks needed to fit the request length.

Abstract: A magnetic disk drive with a caching system includes an intelligent interface to communicate with a host, a magnetic disk and a cache memory to buffer data transferred to and from the host. The caching system maximizes drive performance based on past access history. The caching system alters execution of commands by coalescing commands or executing internal commands in parallel. The caching system anticipates data requests by using a prefetch to store data that may be requested. The caching system divides the cache memory into segments to store multiple streams of data. The number of segments may be continuously adapted according to the types of access to maximize performance by maintaining a segment for each sequential stream of data. The caching system uses a dynamic priority list to determine segments to maintain and discard. Each segment is monitored to determine access types such as sequential, random, and repeating.

Abstract: A disk drive with a disk having a servo pattern including a special "calibration track" wherein a plurality of calibration burst pairs are recorded on a spiral centerline to define null points that are radially shifted from a burst pair centerline by precise, predefined or subsequently measured, fractional track amounts to collectively provide accurate information about servo signal values generated as a function of real displacement. The calibration burst pairs beneficially allow for calibrating the PES signal after the drive is removed from the servowriter during a manufacturing phase called Intelligent Burn-In. The calibration bursts are recorded on a spiral to reduce the recording time and are preferably written in data regions so that they are disposable and may be selectively written over with data to maximize storage space. Some or all of the calibration burst pairs may be retained for a subsequent recalibration.

Abstract: The disk drive provides a method of adaptively managing a cache segment divided into chunks by defining an unavailable data type to be stored in an element of a chunk array which indicates that the chunk is not available, and defining an available data type to be stored in an element of the chunk array that indicates the chunk is available and that indicates the number of consecutive chunks that are available. The disk drive also computes a number of chunks needed to fit the request length and scans the chunk array to find a first available element whose available data type meets a predetermined criteria for the number of chunks needed to fit the request length.

Abstract: A mass storage system made of flash electrically erasable and programmable read only memory ("EEPROM") cells organized into blocks, the blocks in turn being grouped into memory banks, is managed to even out the numbers of erase and rewrite cycles experienced by the memory banks in order to extend the service lifetime of the memory system. Since this type of memory cell becomes unusable after a finite number of erase and rewrite cycles, although in the tens of thousands of cycles, uneven use of the memory banks is avoided so that the entire memory does not become inoperative because one of its banks has reached its end of life while others of the banks are little used. Relative use of the memory banks is monitored and, in response to detection of uneven use, have their physical addresses periodically swapped for each other in order to even out their use over the lifetime of the memory.

Abstract: A method of deriving optimum read channel parameters for use in reading servo sector data from a disk drive having a head mounted on an actuator, a read channel including a preamplifier, a disk having a plurality of tracks, each track having multiple sequentially active servo sectors, a sampled signal head positioning servo controller to control the actuator position, a microprocessor, and a memory. The first step is to store default values and variable test values associated with read channel parameters. The microprocessor is programmed to detect certain servo errors which may occur. The read channel parameters are initially set to the default values in order to ensure that the disk drive can properly perform a seek. A series of seeks is then performed in alternating directions over a band of tracks.

Abstract: A disk drive employs a method for writing a block of data (or multiple blocks of data) to a data region following a defective servo sectors. The disk drive includes a sampled head positioning servo system and a rotating disk with a plurality of data tracks on a surface of the disk. Each data track has multiple spaced-apart sequentially-active servo sectors. Data regions are disposed between the servo sectors. The method includes the step of executing a command to perform a write operation to write a data block to a target data region. A defective servo sector S.sub.n is encountered preceding the target data region during the write operation. The defective servo sector S.sub.n precedes a servo sector S.sub.n+1 and follows a servo sector S.sub.n-1. A timer interval is set to enable a first detection window Dw.sub.n+1 for detecting a field in servo sector S.sub.n+1 . If the field is detected within the detection window Dw.sub.n+1, a field is detected within a detection window Dw.sub.n-1 for the servo sector S.

Abstract: A disk drive controller having a microprocessor and a sampled signal head positioning system measures and stores the relative rotational offsets between heads arranged in a stacked relationship and respective servo wedges on different disk surfaces. The offsets are stored in a table and subsequently applied to a servo wedge detection circuit to ensure that a next sequential wedge is detected after a head switch.

Abstract: The disk drive provides a method of adaptively managing a cache segment divided into chunks by defining an unavailable data type to be stored in an element of a chunk array which indicates that the chunk is not available, and defining an available data type to be stored in an element of the chunk array that indicates the chunk is available and that indicates the number of consecutive chunks that are available. The disk drive also computes a number of chunks needed to fit the request length and scans the chunk array to find a first available element whose available data type meets a predetermined criteria for the number of chunks needed to fit the request length.

Abstract: A head stack assembly for mounting to a pivot bearing cartridge in a disk drive includes a coil having opposite electrical ends and a unitary molded plastic E-block fabricated from a first thermoplastic material containing electrically conductive filler material such that the E-block is electrically conductive. The E-block defines a generally cylindrically shaped body portion and a plurality of elongated arms, the body portion having a pivot bore for receiving the pivot bearing cartridge, a plurality of spaced-apart arm-support regions, and a surface defining a mounting site. Each arm is cantilevered from a respective one of the arm-support regions to project radially away from the pivot bore. The head stack assembly further includes an overmolded coil frame securing the coil to the body portion such that the coil is cantilevered to project radially away from the pivot bore. The overmolded coil frame is fabricated from a second thermoplastic material and is electrically non-conductive.

Abstract: A method of making a head disk assembly using a fixture is disclosed. The head disk assembly includes a base having an interior-horizontal surface and a side wall extending in a direction substantially perpendicular to the horizontal surface, a disk for coupling to the base, and a head for coupling to the base. The disk includes a head facing surface and an outer diameter and the head includes a disk facing surface. The fixture includes a light source for propagating a light beam towards the side wall, a light reflecting structure for receiving the light beam and outputting a reflected light beam, and a control structure for controlling a vertical movement of the light reflecting structure, the light reflecting structure includes a reflecting mirror surface defining an angle with respect to the horizontal surface.

Abstract: In a disk drive having a disk and a sampled track positioning servo system with a plurality of servo tracks spaced apart by a servo track pitch, a method and apparatus for separately determining the pitch of data tracks based on the servo track pitch and address fields located on the servo tracks. By separately optimizing data track pitch and servo track pitch, the design requirements for data density and servo control can be satisfied without the conflict imposed by a fixed relationship of the two track pitch dimensions.

Abstract: The invention is a method of assembling an integrated computer by successively placing various components into an open-top weldment or "tub." The assembly method is particularly suited to rapidly and cost-effectively assembling an integrated computer module in an automated, assembly line environment.

Abstract: A digital-to-analog converter (DAC) is preferably employed to receive a digital input word and provide an analog output signal to a motor driver in a disk drive servo. The digital input word has a plurality of bit positions for establishing a resolution for the DAC. These bit positions define first and second groups of bits. The DAC comprises circuitry responsive to the first group of bits for producing a pair of analog signals defining a common-mode magnitude and a differential magnitude. The common-mode magnitude is a function of the value of the first set of bits and the differential magnitude is a function of the number of bit positions in the first group of bits.

Abstract: A disk drive includes a base, a spindle motor coupled to the base, a disk mounted on the spindle motor, a pivot assembly coupled to the base, and a head stack assembly. The head stack assembly includes an actuator body defining a bore for surrounding the pivot assembly, a supporting surface, and an actuator arm cantilevered from the actuator body and defining a longitudinal axis. The bore defines a pivot axis of the head stack assembly. The pivot assembly includes a stationary member coupled to the base, the stationary member having a length, and a rotatable member positioned on the supporting surface such that the rotatable member is between the stationary member and the supporting surface. The stationary member and the rotatable member define a projecting member and a recessed portion, the projecting member and the recessed portion interacting to allow the head stack assembly to pivot about the pivot axis.