Seagate Technology Incorporated

Jpmorgan Chase Bank, As Collateral Agent

Beng Wee Quak

Myint Ngwe

Kah Liang Gan

Teck Khoon Lim

Ming Zhong Ding

Kian Keong Ooi

Wei Loon Ng

Song Wee Teo

Kwee Teck Say

KianKeong Ooi

Quek Leong Choo

Jack Ming Teng

Beng Theam Ko

Wing Hung Chan

Chiap Heok Ang

MingZhong Ding

Niroot Jierapipatanakul

YongPeng Chng

YangQuan Chen

Eng Hock Lim

Michael Joo Chiang Toh

Wing Kong Chiang

Louis Seng Hong Pang

Patrick Tai Heng Wong

Swee Kieong Choo

Chee Suan Low

Wesley Wing Hung Chan

Kok Hoe Chia

Soon Wah Leow

David L Schell

ChoonKiat Lim

Choon Wei Ng

WeiLoon Ng

ShuangQuan Min

Ricky Wei Watt Yeo

KokHoe Chia

Patrick TaiHeng Wong

Poh Lye Lim

Victor Chi Siang Choo

Daniel Eugene Hobson

James Lai Kein Chang

Liu Li

Chris Thomas Settje

Shuang Quan Min

Lan Xia

Lee Ling Tan

Ricky WeiWatt Yeo

Khong Mau Ling

Bernard Tuang Liang Lim

Ying Ee Yip

Hwee Peng Teo

Alan Choon Tan

Niroot Jicrapipalanakul

Wei Wei Sun

Lian Chong Kwek

Ng Wei Loon

Kok Seng Lim

Teng Hou Sebastian Chua

Chee Wai Lum

Bernard Tuang Lim

Yang Quan Chen

An apparatus and method for selecting physical cylinders (cylinders accessible for read/write operations) in a disc drive is provided. The disc drive includes at least one rotatable disc. The disc drive also includes a first head, which is positionable adjacent a first disc surface, and a second head, which is positionable adjacent a second disc surface. The first disc surface has a first plurality of greycode tracks and the second disc surface has a second plurality of greycode tracks. Each greycode track of the second plurality of greycode tracks corresponds to a different greycode track of the first plurality of greycode tracks, thereby forming a plurality of greycode cylinders, with each greycode cylinder of the plurality of greycode cylinders including a pair of corresponding greycode tracks. The physical cylinders are a subset (less than all) of the plurality of the greycode cylinders. The method of selecting the physical cylinders includes determining whether the first plurality of greycode tracks or the second plurality of greycode tracks demonstrates greater track eccentricity, to thereby obtain a maximum track eccentricity surface and a corresponding maximum eccentricity head. The maximum track eccentricity surface is one of the first and second disc surfaces and the maximum eccentricity head is a corresponding one of the first and second heads. The maximum eccentricity head is used to locate at least one of the physical cylinders.

Selecting physical cylinders in a disc drive employing discs with pre-written servo patterns

A method of categorizing magnitudes of thermal asperities in a read-back signal of a data storage system includes receiving the read-back signal from a location containing a thermal asperity. A peak magnitude signal is generated from the read-back signal. A threshold signal is generated using a variable threshold generator. The peak magnitude signal is compared to the threshold signal and a magnitude of the thermal asperity is categorized as a function of the comparison.

Thermal asperity multi-threshold algorithm using the read/write channel

A method of tuning a bias parameter for a magnetoresistive head in a data storage system includes the step of identifying, from multiple possible bias parameter values, a smallest bias parameter value for the magnetoresistive head which both maintains a bit error rate above a predetermined threshold bit error rate, and which satisfies a second criteria. The method then includes the step of setting an operational bias parameter value for the magnetoresistive head to the identified smallest bias parameter value. Also disclosed are data storage systems, or controllers which are connectable to or included with data storage systems, configured to implement the methods.

Method and apparatus for tuning a magnetoresistive bias parameter in a data storage system

A method of handling resonance effects on disc drives includes the steps of monitoring a position error signal (PES) for an actuator arm of a disc drive, generating a feedforward compensation signal from the PES using a bandpass filter, and applying the compensation signal to a servo control signal. The bandpass filter has a center frequency set to a known resonance frequency. A disc drive includes an actuator assembly including an arm for carrying a head in a transducing relation with respect to a disc in response to a control signal, and a controller that monitors a PES for the arm and generates the control signal. The controller includes a servo controller that generates a servo control signal from the PES, and a feedforward compensation element which bandpass filters the PES to generate a compensation signal which is combined with the servo control signal to generate the control signal.

Method and apparatus for handling resonance effects in disc drives using active damping

An information handling system, such as a disc drive, includes a base, a disc stack rotatably attached to the base, and an actuator assembly movably attached to the base. A region of the disc stack is identified as a parking band, and when power is not provided to the disc drive, the actuator assembly is held in a parked position within the parking band by an actuator latch. The actuator latch and actuator assembly have different resonant frequencies based on several environmental elements near the actuator assembly, including the temperature of the environment in the disc enclosure. The actuator assembly is unlatched by measuring the environmental element near the actuator assembly and applying an alternating current to a voice coil coupled to the actuator. The frequency of the alternating current applied to the actuator assembly during the unlatching procedure is near the resonant frequency of the actuator assembly in the measured environment.

Adaptive temperature compensated AC unlatch algorithm

A data storage device has a plurality of head/surface combinations with different data track densities on at least two surfaces. A minimum head quality is established for the data storage apparatus. Head quality is identified for each of the heads at each of a plurality of track densities. A tuned track density is selected for each surface based on the track density that corresponds to a head quality.

Tuning track density for data storage device

A disc drive includes a base and a disc rotatably attached to the base. The disc drive is formatted by obtaining a list of defective sector entries, determining a first location of selected information based on skipping the defective sectors within the list of defective sector entries, and calculating a second location for selected information. At least one sector to skip is added before the second location of selected information to move the selected information from the first position to the second position. The added sectors may be designated as defective sectors. By adding the at least one sector to skip, the second position of the information is moved or slipped.

Disc drive with fake defect entries

According to one embodiment of the present invention a disc controller in a disc drive includes a cache memory and a control circuit. The control circuit is configured to identify an operating system of a host computer coupled to the disc drive, select a segmentation level for the cache memory based on the identified operating system, and store information in the cache memory according to the segmentation level. According to another embodiment of the present invention a cache memory in a disc drive is operated by identifying an operating system of a host computer coupled to the disc drive, selecting a segmentation level for the cache memory based on the identified operating system, and storing information in the cache memory according to the segmentation level. The operating system is identified by reading a partition type from a master boot record stored in a disc in the disc drive.

Adaptable cache for disc drive

A method for writing servo patterns on at least one disc in a disc drive that has a first set of tracks and a second set of tracks on a major surface of the disc includes stepping between the tracks of the first set of tracks at a first constant angle, and stepping between the tracks of the second set of tracks at a second constant angle. Stepping between tracks in the first group or the second group includes selecting two adjacent tracks from either the first group of tracks or the second group of tracks, and determining the angle through which an actuator assembly must be rotated between the two adjacent tracks selected to produce a selected track pitch. The method produces a disc for a disc drive with a first set of tracks, and a second set of tracks in which the track pitch varies across the set of tracks.

Segmented constant angle trackpitch

A method for writing servo information to a disc rotatably mounted to a spindle motor. A measured cage frequency is obtained from a written reference track, from which an actual cage frequency is predicted. The predicted cage frequency is then used to derive compensated position commands. During a servo write interval, the compensated position commands are used to control the head such that the head follows the disc movements caused by the cage frequency.

Prediction and cancellation of cage frequency in a disc drive

A method of implementing an automatic acoustic management feature for a disc drive includes receiving an acoustic/performance compromising factor from a host, tuning disc drive performance by applying the factor to a control parameter to generate a modified control parameter, and executing a loop for controlling a disc drive operation using the modified control parameter. In another embodiment, a disc drive has a base, a rotatable disc, an actuator assembly with an arm for carrying a head in transducing relation to the disc in response to a control signal, a receiver for receiving an acoustic/performance compromising factor, and a controller that monitors the position of the arm and generates the control signal. The controller executes a seeking control loop having a control parameter modified by applying a compromising factor to the parameter to tune the acoustic performance of the drive.

Automatic acoustic management system for a disc drive

A method and apparatus for detecting and recovering from head instability in a magneto-resistive (MR) transducer head of a disc-drive system. A head-instability-recovery circuit is described for use in disc drive to recover from a head-instability condition of an MR transducer head. This circuit includes a controller and a current source that supplies current to the MR head. The current source is controlled to supply a nominal amount of current to the MR head when operating in a normal mode, and to supply one or more current bursts having a current above the nominal supply current in order to recover from the head-instability condition. Also described is a method for recovering from a transducer-instability condition of an MR transducer of a disc drive, including detecting a situation that indicates a head-instability-recovery operation is desired, and performing the head-instability-recovery operation.

Self-diagnostic MR head recovery

A method for minimizing unbalance in the disc pack of a disc drive where the unbalance of the spindle motor is quantified and incorporated into the biasing assembly of the disc pack. In the assembly process, the discs are biased in a manner such that the unbalance of the spindle motor is considered.

Disc biasing scheme to minimize single plane unbalance for hard disc drives

A writer coil in a data head of a data storage system is tested by coupling detection circuitry to the writer coil and driving the writer coil with a periodic pulse signal generated by the detection circuitry. As a result, voltage is generated, with the detection circuitry, as a function of an inductance of the writer coil. An inductance of the writer coil is calculated as a function of the generated voltage. Electrical short circuits and discontinuities in the writer coil are identified as a function of the calculated inductance.

Data head writer coil testing

A servo writer writes servo information to at least one disc of a head disc assembly. The servo writer includes a clock head that writes a clock track to the at least one disc and generates a clock signal when the clock head reads the clock track on the at least one disc. A servo pattern generator writes servo patterns to the at least one disc in response to the clock signal generated by the clock head reading the clock track on the at least one disc. The servo track writer also includes a phase lock loop clock generator which synchronizes to the clock track and produces the clock signal for the servo pattern generator.

Method for servo writing servo pattern at a desired speed

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Singapore, Singapore

Beng Wee Quak