Abstract: In a disk drive using a write-wide inductive write element and a read-narrow magneto-resistive read element within a head transducer assembly for writing and reading magnetic patterns on a rotating magnetic storage disk in a plurality of concentric tracks, a track pattern formed in each concentric track includes embedded servo wedges wherein each wedge includes a servo position portion which is offset from a centerline of both the servo sector and a following user data sector by an amount related to offset between the inductive write and magneto-resistive elements of the head transducer assembly. Furthermore, the servo sector contains four servo bursts. The servo bursts are arranged such that each sequential burst is offset from a previous burst by a fractional offset increment. The fractional offset increment is typically one-third of a track pitch.

Abstract: Write precomposition optimization for a partial response maximum likelihood ("PRME") magnetic recording chapel adapted to a mass production environment. Optimal write precompensation may be determined by writing a tribit data pattern known to produce worst case nonlinear transition shift ("NLTS") onto a magnetic recording medium; reading back the recorded data pattern; and calculating the mean-squared error ("MSE") for one or more of the equalized data sample levels associated with the PRML channel to be optimized. The writing and reading back process is repeated with varying amounts of precompensation applied to the written pattern. The optimal amount of write precompensation is determined eider by minimizing the MSE for a selected sample level or by minimizing MSE between the middle and the upper or lower of the ternary PRML sample levels.

Abstract: A hydrodynamic bearing journaling a shaft includes a rotatable bushing journaling the shaft and thrust plates on the shaft at opposite ends of the bushing. The bushing is encased in a cylindrical sleeve. Lubricant containing clearance spaces are formed between the shaft, bushing, sleeve, and thrust plates. An internal radial chamber in the sleeve between the bushing and sleeve stores lubricant and collects foreign particles. Radial ports through the bushing provide for flow of lubricant between the journal bearing and the shaft and thrust plates.

Abstract: A method for forming a precision groove in a cylindrical surface of an article such as a sleeve-shaft hydrodynamic journal bearing system includes the steps of: aligning a groove-forming machine to an axial datum plane of the article defined in a spaced-apart relation with the cylindrical surface by a predetermined nominal first dimension, translating the groove-forming machine in an axial direction toward and upon a first edge of the cylindrical surface by an amount equal to the predetermined nominal first dimension and thereupon forming a first groove axial step segment in the cylindrical surface until a second predetermined axial datum plane is reached, simultaneously axially translating and rotating the groove-forming machine from the second axial datum plane until a third predetermined axial datum plane is reached and thereupon forming the precision groove pattern in the cylindrical surface between the second axial datum plane and the third axial datum plane, and axially translating the groove-forming ma

Abstract: A method, and associated apparatus, or applying fluid lubricant to hydrodynamic bearing. Clearance spaces of the bearing which are to be filled with the fluid lubricant are evacuated. The fluid lubricant is then applied to the clearance spaces. Once the fluid lubricant has been applied to the clearance spaces, or concurrent therewith, the clearance spaces are returned to ambient pressure levels. Any pockets of air, or other gas, trapped within the bearing are collapsed as the clearance spaces are returned to the ambient pressure levels. The method is amenable to a high volume, assembly line-like process wherein large numbers of bearings may be filled with the fluid lubricant in a short period of time. A conveyor conveys the bearings into a pool of fluid lubricant in a vacuum tank having a pressure level adjustable between an ambient pressure level and an evacuated pressure level, through the pool of fluid lubricant, beyond the pool, and out of the vacuum tank.

Abstract: Synchronous detection of fine position servo burst information with a data transducer having an electrical width not less than about two-thirds a width of a data track within a partial response maximum likelihood (PRML) data channel is disclosed. The servo burst information is recorded on a storage medium as a pair or series of fractional-track-width sinewave concurrent burst patterns and includes an on-track phase generating a position error signal which varies linearly with head displacement about track centerline and at least one off-track phase generating a position error signal which varies linearly with head displacement about a position related to track boundary.

Abstract: A soft adjacent layer biased magnetoresistive ("MR") device, and a method for producing the same, which incorporates a natural flux closure design utilizing coplanar thin film permanent magnets to stabilize the device while obviating induced domain walls in the magnetoresistive and soft adjacent layers ("SAL"). The device structure includes an SAL film and overlying magnetic spacer layer ("MSL") in conjunction with an MR film to produce an SAL biased magnetoresistive structure ("MRS") with the MR layer patterned to a shortened length with respect to the SAL and MSL layers. A non-magnetic metal or dielectric separation layer of on the order of 20-300 angstroms (".ANG.") is then deposited over the MSL layer and the sides of the MR layer followed by the deposition of permanent magnet layer portions substantially coplanar with the MR layer to produce a low energy equilibria device with high sensitivity and superior signal output.

Abstract: An encoding system uses a modified 8/9 rate modulation code to encode 8-bit data symbols into 9-bit cells in a conventional manner in accordance with the modified code and 9-bit ECC symbols into 10-bit cells by (i) encoding 8 bits of the symbol into a 9-bit cell in accordance with the modified code, and (ii) inserting into the 9-bit cell the remaining, that is, the non-encoded, bit of the ECC symbol. The system reproduces the 8-bit data symbols by decoding the 9-bit cells in a conventional manner in accordance with the modified code, and the 9-bit ECC symbols by (i) removing from the associated 10-bit cell the bit inserted during encoding, (ii) decoding the remaining 9 bits to reproduce 8 bits of the symbol, and (iii) inserting into the 8 bits the bit that was earlier removed. In an exemplary embodiment, the 8 least significant bits of the ECC symbol are encoded using the modified 8/9 rate code. The 9 bits produced by the code are used essentially as the first "c" bits and last "10-c" bits of a 10-bit cell.

Abstract: A technique for verifying a pre-recorded header in a disk drive uses verification history to protect against errors that can cause verification failure. A head number, sector address, and upper track address (track MSB) are read from the disk and compared with corresponding expected values. The results of the 5 most recent comparisons are saved in three 5-bit memories. During each verification, a programmable selection and comparison circuit selects M of the stored indicators and determines whether at least N of them indicate a match. If so, the corresponding field is declared to be correctly verified, so that subsequent reads or writes to data blocks within the corresponding sector are allowed to proceed.

Abstract: An apparatus for detecting off-track positioning of a disk read/write head seeking a selected data track on a disk having data tracks with embedded servo burst patterns recorded thereon. The apparatus comprises a compare and select component, a charge redistribution A/D converter circuit and an off-track controller. The compare and select component compares and selects from among voltage values corresponding to the servo bursts a pair best representing track centerline as a first servo signal and a second servo signal and determines which of the servo signals is greater. The charge redistribution analog-to-digital (A/D) converter circuit determines if the normalized track position exceeds a position threshold representing a percentage of the normalized track position distinguishing on-track from off-track position through the use of an internal binary-weighted, switched capacitor array DAC and a comparator.

Abstract: A self-contained hydrodynamic bearing unit includes a shaft and a shaft housing defining an opening for receiving the shaft for relative rotation. The shaft and bearing define at least one radial hydrodynamic bearing and an annular thrust bearing, formed as a disk portion extending radially outward of a main cylindrical surface of the shaft which cooperates with an adjacent annular face of the shaft housing. A gap between an outer cylindrical wall of the thrust bearing disk portion and an adjacently facing cylindrical surface of the shaft housing provides a primary annular capillary seal segment. An annular bushing ring extends from the housing radially inwardly to enclose the thrust bearing disk, and cooperates with an adjacent outer face of the thrust bearing disk to provide a secondary containment capillary seal segment. Normally, lubricating liquid is in the bearing unit at the radial hydrodynamic bearing, at the hydrodynamic thrust bearing and in the primary annular capillary seal segment.

Abstract: A seal for a hydrodynamic bearing unit having a shaft and a sleeve includes a seal ring secured to the shaft and extending radially outwardly of the pair of spaced-apart hydrodynamic journal bearings defined between the seal ring and a thrust plate. The seal ring adjacently faces adjacent radial and axial portions of the sleeve. An annular taper capillary seal is defined between a diverging outer wall surface of the seal ring and the adjacent axial portion of the sleeve. A containment ring extends from the sleeve to surround a radial wall portion of the seal ring adjacent to an opening of the taper capillary seal and forms a secondary containment seal opening toward the shaft for preventing escape of the hydrodynamic bearing lubricant.

Abstract: A spindle shaft attachment technique for a disk drive includes a conical tip formed on, or added to, the top of the spindle shaft in order that it might be embedded in or contact a substantially planar, interior surface of the HDA cover at a location determined by the perpendicularity of the spindle as set by the baseplate without forcing the top of the spindle shaft to a predetermined screw hole or recessed cone location on the cover. The spindle shaft attachment technique disclosed allows for use of a relatively longer spindle shaft for a given height form factor drive and, therefore, allows a greater spacing between upper and lower spindle bearings resulting in greater stiffness and an increased rocking mode frequency.

Abstract: Plural embedded servo sector sets are written as a single operation by a servo writer during manufacture of a hard disk drive. Later, the disk drive electronics performs a self scan and selects one good set of embedded servo sectors and erases all other sets, thereby decreasing the number of servo sector rewrites during manufacture and reducing manufacturing time and costs.

Abstract: A "zero phase start" optimization circuit for a Partial Response, Maximum Likelihood ("PRML") data channel dynamically determines a more optimal starting phase for the timing recovery process in a synchronous communication or storage system. The disclosed circuit includes a quantizer, a summing junction, either an absolute value or squaring function, and an integrator. A firmware based optimization routine causes a timing control loop to go through a series of timing acquisition modes, each time starting a clocking oscillator at different phase. The optimization circuit calculates the mean squared error between actual and expected sample values from a known frequency preamble pattern for each timing acquisition. The minimum MSE value corresponds to a more optimal starting phase for the timing control loop oscillator.

Abstract: An integrated digital logic circuit includes a free-running secondary clock oscillator for generating free-running clocking pulses and a frequency-stabilized master oscillator for generating primary clocking pulses. A clock signal selector selects and puts out either the secondary clocking pulses or the primary clocking pulses depending upon integrated circuit operations/applications. A method for rapidly generating clocking signals during an integrated circuit start-up interval is also described.

Abstract: A disk drive command queue reordering method includes calculation of least-latency and accounts for dependencies of I/O commands in the queue to avoid data hazards with respect to reordering of I/O commands. Command queue representation is augmented by a graph structure representing dependencies of queue commands. Computational overhead associated with constructing, maintaining, and executing graph flow analysis relative to the dependency graph is sufficiently low to allow interleaved operation with higher level disk drive functions such as timely interaction with the host device. The disclosure includes a method of calculating and maintaining the dependency information in a command queue and using this information to constrain command reordering in a time and computationally efficient manner.

Abstract: A digital output magnetoresistive ("DOMR") head for magnetic playback comprising one or more "pinned" magnetic layers having magnetic polar direction which does not rotate under an external field from the media, and a magnetic digital switching layer formed using either shape or crystalline anisotropy such that it has an easy axis parallel to the magnetic direction of the pinned layer or layers and two stable magnetization directions, parallel or antiparallel to the magnetization polar direction of the pinned layer or layers. Because of this dual stable state configuration the DOMR head produces a substantially digital output when reading magnetic information.

Abstract: Apparatus and method for detecting occurrence of a non-pulse interval of predetermined length between a beginning pulse and an ending pulse as included within a sequence comprising a unique timing mark within a stream of pulses supplied from a source with a state machine. The method of the state machine includes the the steps of:advancing through a plurality of nominal states marking in time the non-pulse interval,branching to one of a plurality of available spurious pulse states from one of the nominal states upon detection of a first unexpected pulse,returning to advance through predetermined remaining ones of the plurality of nominal states following detection of the first unexpected pulse,reaching a completion state following the nominal states if only the first unexpected pulse is detected, andreaching an error state following a branch to another one of the plurality of available spurious pulse states upon detection of a second unexpected pulse within the non-pulse interval.

Abstract: A suspension load beam for a rigid disk drive. The load beam has a central load beam member having a flexure supporting surface and an opposing surface, and rails disposed along the sides of the central member. The rails form channels extending away from the flexure supporting surface at a proximal end of the central member, and the rails extend away from the opposing surface at a distal end of the central member. The rails thereby have the advantageous characteristics of "upswept" rails at the distal end of the load beam while retaining the advantageous characteristics of "reverse" rails at the proximal end of the load beam.