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 storage disk drive having a servo burst pattern which asymmetrically increases the linear region in which a read head may be micro-jogged from a burst pair center line to align the read head with a data track. The innovative servo pattern comprises a first pair of servo bursts that define a first burst pair centerline for writing a particular data track to a data track side of the first centerline, and a second pair of servo bursts collectively define a second burst pair centerline that is positioned to the data track side of the first burst pair centerline and is sufficiently close to the first burst pair center line so that the read head "sees" the second pair of servo bursts before "losing" the first pair of servo bursts when micro-jogged to the data track side for reading. The second burst pair centerline should be no farther from the first burst pair centerline than the linear read width of the read head.

Abstract: An initialization for runout cancellation for a hard disk drive such as a Small Computer System Interface (SCSI) hard disk drive. The hard disk drive at a servo sample rate updates a set of state variables. At an index wedge the state variables are stored to a memory. Upon a command to perform a head switch the hard disk reads the previously stored state variables from the memory. The previously stored state variables are used to adjust the repeatable runout based on the location of a head relative to an index wedge.

Abstract: A magnetic disk drive with a head stack assembly includes a body portion, a main flex circuit, an actuator arm cantilevered from the body portion and a head gimbal assembly supported at the actuator arm. The actuator arm includes a proximal end and a distal end, a first side surface and a second side surface A first array of conductive traces is supported at the first side surface and a second array of conductive traces supported at the second side surface. Each conductive trace includes a proximal conductive pad proximate to the proximal end of the actuator arm, a distal conductive pad proximate to the distal end of the actuator arm and a conductive path between the proximal and distal conductive pads. The head gimbal assembly includes a load beam having a base region abutting the actuator arm, a head coupled to the load beam, first and a second array of base region conductive pads, each array of base region conductive pads positioned on the base region and for electrically connecting to the head.

Abstract: A head disk assembly for a hard disk drive having a mechanical actuator latch subassembly. The head disk assembly includes an enclosure, a disk, a pivot bearing cartridge, and a head stack assembly. The enclosure includes a base that preferably includes integral side walls. The disk has a recording surface that has an annular landing zone. The head stack assembly includes a head supported to be moved radially relative to the recording surface and to be brought to rest at a position in the landing zone. Significantly, the head disk assembly also includes a unitary latch base member and a unitary pivot latch member. The unitary latch base member has a mounting portion for mounting the latch base member to the base, an arm extending parallel to the major interior-facing surface, an inner crash stop post including an engaging end, and a pivot post. The arm also includes a spring holding post. The unitary pivot latch member has a bore surrounding the pivot post to allow pivot motion of the pivot latch member.

Abstract: A method is disclosed for calibrating a position error signal (PES) to overcome the problem of an amplitude signal that varies as a non-linear function of real displacement when the read transducer is positioned to either side of a null position where the PES equals zero. The amplitude signal and resulting PES is notably nonlinear while reading servo burst information with a Magneto-Resistive (MR) head which has nonlinear magnetic characteristics. The calibration according to this method may be performed at anytime without need for real displacement information from a servo track writer or any sort of special calibration track. The method involves positioning the MR head to a plurality of nominal partial track displacements on either side of the null position, measuring an open loop gain value for a particular frequency at each of the displacements, deriving the coefficients of a 3.sup.rd order polynomial "gain" curve that best fits the data, integrating the "gain" curve using the coefficients to obtain a 4.

Abstract: A magnetic disk which includes a thin film magnetic layer resistant to thermal erasures caused by a rise in localized temperature in the disk due to head disk interference includes a substrate having a thermal diffusivity of less than about 2.times.10.sup.-6 m.sup.2 /sec and a magnetic layer for storing information which is subject to erasure upon such use in localized temperature generated by the head disk interference. An underlayer below the magnetic layer is provided for orienting crystalline structure of the magnetic layer, and the heat sink layer directly above the substrate and directly below the underlayer has a single material such as chromium. The heat sink layer has sufficient thermal diffusivity and sufficient thickness for dissipating heat generated by the rise in localized temperature caused by head disk interference to prevent the erasure of stored information in the magnetic layer.

Abstract: A method is provided for managing a cache in a disk drive having an intelligent interface for communicating with a host. The drive includes a magnetic disk, and the cache is divisible into a number of segments, and employs a cache control structure including cache parameters. The drive receives a first command and a second command. The method comprises the steps of: performing a scan of the cache to assign the first command to a segment; compensating the cache parameters in response to the scan; and performing a scan to assign the second command to a cache segment prior to caching of data requested in the first command.

Abstract: A disk drive is connectable to a power supply having a fixed DC voltage. The disk drive includes a voice coil motor. The fixed DC voltage is supplied to a first node. A capacitor is coupled between the first node and a second node and is charged to approximately the fixed DC voltage by grounding the second node while the disk drive performs a track following operation. The DC voltage of the first node is increased to an increased DC voltage greater than the fixed DC voltage by providing the fixed DC voltage to the second node while to the disk drive performs a track seeking operation. The first node is de-coupled from the fixed DC voltage while the DC voltage of the first node is greater than the fixed DC voltage. The DC voltage of the first node is provided to the voice coil motor. The increased VCM voltage allows faster access times and more efficient VCM operation.

Abstract: A disk drive has an intelligent interface for communicating with a host, a magnetic disk, and a cache. The cache is divisible into a number of segments, with each segment having a cache access type. The number of segments may be varied in practice of a method for adaptively segmenting the cache. The method comprises the steps of: (a) calculating a plurality of caching factors while processing commands from the host; and (b) regularly determining whether to change the number of segments wherein an increase of the number of segments is effected based on a weighed weighing of the plurality of caching factors.

Abstract: A disk drive having an embedded servo disk format preferably having a fixed-number of radial servo sample wedges per track, in which data blocks are located independently of the servo sample wedge locations of any particular track, and can be split around servo sample wedges. Thus, a fraction of a data block, or more than one data block, can be written between consecutive servo sample wedges, beginning almost anywhere in a data wedge. Each data sector has an associated identification (ID) field that includes at least one segment descriptor. Each segment descriptor describes the data segments into which a data block can be split. Provision is made for as many segment descriptors as there can be data segments for a data block. In general, a segment descriptor is a multi-bit digital signal that defines the absolute or relative location of split data segments (or, alternatively, the absolute or relative length of split data segments, from which the location can be determined).

Abstract: A method provides for managing commands received by a disk drive via an intelligent interface from a host. The drive has a magnetic disk, and a cache with the cache being divisible into a number of segments. The cache employs a cache control structure including a cache environment variable. The drive receives a first command that requests data and a second command. The method comprises the steps of: processing the first command and caching only the requested data from the disk drive; and processing the second command and caching prefetched data for the second command if the second command is determined to be sequential with the first command.

Abstract: A magnetic disk drive with a head stack assembly having a pass-through flex circuit cable is disclosed. The pass-through flex circuit cable is mounted to a side of the head stack assembly to extend straight forward in an initial unfolded position during handling and assembly and to then be folded over into a final position in a substantially opposite direction and with a desired flex cable trajectory. The head stack assembly includes a post, preferably of rectangular profile, that is integrally formed and spaced away from the actuator body. An outer surface of the post defines the flex cable trajectory. The flex circuit cable, located in the space between the actuator body and the post, extends past the post in the initial position and wraps around the post in the final folded over position. The flex circuit cable is secured to the post in the final folded over position, preferably with a flex clip that removably mounts to the post.

Abstract: The invention is a method of calibrating a position error signal (PES) to overcome the problem of a measured displacement or PES that varies as a non-linear function of real displacement when the read transducer is positioned to either side of a null position where the PES equals zero. The PES is notably nonlinear while reading servo burst information with a Magneto-Resistive (MR) head which has nonlinear magnetic characteristics. The method uniquely calibrates the measured PES to provide a corrected PES without requiring any knowledge of the actual displacement from the position where the measured PES equals 0. The calibration according to this method, therefore, may be performed at anytime without need for real displacement information from a servowriter or any sort of special calibration track.

Abstract: The invention relates generally to rotating magnetic storage disk drive and, more particularly, to a method of seamlessly recording circumferentially overlapping servo bursts on a magnetic disk with successive passes of a write head that is guided by a servo track writer wherein the servo bursts are contained in at least two servo burst groups that each have at least one circumferential burst position which may contain a servo burst.

Abstract: A method and apparatus for texturing a landing zone on a substrate of a magnetic disk to reduce stiction between a magnetic transducer head and the disk is provided. The method includes projecting discrete pressurized fluid droplets to impact a substrate surface of the substrate with sufficient momentum to form cavities in a selected annular area of the substrate surface, the selected annular area with cavities therein being of sufficient width to provide a textured landing zone for the magnetic transducer head. A magnetic disk for storing data readable by a transducer head is also provided. The disk includes a rigid substrate. A textured landing zone is provided on the disk for engaging the transducer head. The textured landing zone is formed by the steps of directing a stream of discrete pressurized fluid droplets against the substrate to create roughness therein and moving the substrate and stream of droplets relative to one another in order to create an annular area of roughness.

Abstract: The invention is a method of calibrating a position error signal (PES) to overcome the problem of a measured displacement or PES that varies as a non-linear function of real displacement when the read transducer is positioned to either side of a null position where the PES equals zero. The PES is notably nonlinear while reading servo burst information with a Magneto-Resistive (MR) head which has nonlinear magnetic characteristics. The method uniquely calibrates the measured PES to provide a corrected PES by measuring the PES while slowly moving the MR head at a constant radial velocity, determining the actual displacement corresponding to each measured PES, and comparing the measured PES with the ideal PES for the corresponding displacement to develop a correction table for providing a corrected PES when given a measured PES. The method uniquely relies on the standard servo burst data and may, therefore, be performed at anytime without need for a servowriter or any sort of special calibration track.

Abstract: A hard disk drive has an intelligent interface for communicating with a host, a magnetic disk, disk side programs and host side programs, and a cache. The cache is divisible into a number of segments, and the number of segments may be varied. The cache employs a cache control structure including a cache entry table, and the hard disk drive receives commands from the host in a queue. The method comprises the steps of. (a) receiving a first command and a second command from the host; (b) determining a scan first state; (c) determining if there are any commands in the queue; (d) waiting for a first command to complete and performing a seek if there are no commands in the queue and the scan first state is false; (e) performing a scan of the cache entry table to assign the second command to a segment; and () checking if a seek is needed for the second command and if a seek is needed for the second command performing a seek for the second command after the first command has completed.

Abstract: The invention resides in a magnetic disk drive having a load beam assembly that forms a part of a head gimbal assembly and head stack assembly in a magnetic disk drive.The load beam assembly is uniquely mass balanced to prevent head slap by preventing an acceleration in the Z-direction from causing the transducer head to separate from the disk. The load beam assembly is preferably mass balanced by providing a load beam balancing member that is rigidly connected to the elongated load beam about a transverse axis of the hinge member. The balancing member can form the balancing mass or the balancing member can carry a discrete balancing mass. The balancing member may be divided into two halves that move on either side of the base portion, but is preferably comprised of a narrow, centrally located member that moves within an aperture formed in the base portion. The mass balanced load beam assembly can beneficially be manufactured from the same stainless steel sheets used to form conventional load beam assemblies.

Abstract: An integrated circuit includes an ECC encoder having a normal mode of operation and a test mode of operation. During the test mode, the encoder is operated as a test pattern generator for computing a test pattern that exhaustively stimulates data paths, memory structures and other logic functions on the integrated circuit. A signature of responses to the test pattern can then be computed and compared to a known "correct" signature to determine whether timing faults and other types of faults exist in the integrated circuit. A disk controller chip based on such an integrated circuit can, in addition to testing its own on-chip data paths, memory structures and other logic functions, supply a test pattern to a read/write channel chip and other components on a printed circuit board assembly of a disk drive.