Abstract: A position control system for a magnetic head improves servo tracking characteristics in a low frequency range without impairing the stability of seek operations. The position control system is equipped with two integrators: a first integrator 43 and second integrator 45. The gain K3′ of the second integrator 45 is set larger than the gain K3 of the first integrator 43. The first integrator 43 plays the role of offsetting the bias force acting on the magnetic head while the second integrator 45 plays the role of improving the servo tracking characteristics in the low frequency range.

Abstract: Apparatus for detecting defects in a magnetic disk includes a read head including multiple read elements for reading multiple tracks of the disk. Read signals produced by the read elements are received by certifier circuit portions for determining whether any of the read signals includes an indication of a defect in the disk. A monitoring circuit monitors the read elements to detect a malfunctioning read element. The read head position is controlled so that a malfunctioning read element is not used.

Abstract: There is provided a method of parking a hard disk drive head, which can minimize an impact during head parking using an alternating current (AC). This method includes the steps of: determining whether no command is input during a predetermined time in a wake-up mode, or whether a power-off command is input; and moving the head to a parking area by driving an actuator to which the head is attached using an initially-set alternating current, if no command was input during the predetermined time or a power-off command was input. Accordingly, damage to the head and head suspension, caused by the collision of the head with a latch magnet because of an excess acceleration of the actuator during parking, can be prevented.

Abstract: A data zone optimization method and architecture for optimizing the location of the data zone on a data storage disk is disclosed. The data zone is preferably biased toward the outer diameter of the disk, and is referenced to a data zone starting location established proximate a load/unload ramp apparatus. An optimum starting location for the data zone of an initially unformatted data storage disk is preferably determined by contacting the load/unload ramp with the transducer assembly, disengaging the transducer assembly from the ramp, and writing servo information indicative of the data zone starting location at a disk location proximate the ramp and transducer assembly contact point. Servo information indicative of the data zone is written at inner diameter disk location with respect to the optimum data zone starting location. The optimized data zone architecture may have a predetermined or variable data storage capacity.

Abstract: A method, apparatus, or product for a rotating disk storage device. In one embodiment, the apparatus includes a disk, a spindle motor that rotates the disk, a transducer, an actuator arm that can move the transducer, and a controller. The controller can control the movement of the actuator arm to move the transducer across the disk surface from a first track to a second track, and determine a position error signal (PES) at one or more positions between the first and second tracks, where the PES includes a non-repeatable disturbance signal. The controller can iteratively generate a disturbance correction signal at the one or more positions based on the PES, combine the disturbance correction signal with the PES to minimize the non-repeatable disturbance signal to provide a corrected PES, and vary, at the one or more positions, the movement of the transducer as a function of the corrected PES.

Abstract: The magnetic disk apparatus includes a magnetic disk for storing thereinto information; a head equipped with a recording conversion element for writing information into the magnetic disk and a reproducing conversion element for reading information from the magnetic head; an actuator arranged by a suspension for supporting the head so as to move the head on the magnetic disk, and also a drive apparatus for driving the suspension; and a stopper for limiting a movable range of the actuator, whereby a distance between a reproduction element and a recording element is measured and also a track width of the magnetic disk is measured in order to execute a self-servo write operation.

Abstract: Disclosed herein is a head-positioning control system designed to move a head to a target position over a disk used as a recording medium. The system causes an actuator to perform a seek operation, thus moving the disk from a prescribed start position to the target position. The system generates seek profile data representing a motion which the head makes during the seek operation. On the basis of the seek profile data, the gain of the system is estimated. A gain-adjusting value is calculated from the gain thus estimated. The gain-adjusting value is applied, adjusting the gain of the system to an appropriate gain.

Abstract: The temperature of an actuator voice coil in a disc drive is regulated so as to prevent outgassing. In a preferred embodiment, coil temperature is calculated at the beginning of each long seek. If the temperature is determined to be at or below a predetermined “safe” level, temperature rise is not limited and power may be applied to the coil without additional limitations. If, however, coil temperature is determined to be above the “safe” level, proportional control is used to scale back power generation so as to prevent the coil temperature from exceeding the coil's specified temperature limit.

Abstract: A method for improving disk drive performance by adaptively calculating skew values for each drive. During a production phase of the disk drive manufacturing process, skew values are calculated using measured seek times, then implemented to each drive. The calculation scheme permits slipped revolutions to occur during a percentage of the time so that skew values are not so high as to hinder high performance.

Abstract: The position information of the magnetic head is generated also from the data area to improve the positioning accuracy. The magnetic disk drive has a function of oscillating the magnetic head in the radial direction in the data area at a specific frequency and a function of detecting a read signal during the execution of the oscillation function and detects position information of the magnetic head from the detected read signal. The magnetic head position control can be performed in the data area. The magnetic head position signal not dependent on the frequency of a sampling signal generated from the servo information area can be generated. This in turn improves the data recording density and allows a highly precise position control of the magnetic head, thus improving the reliability of the magnetic disk drive.

Abstract: A sector servo type magnetic disk apparatus is provided with, in addition to servo signals, a sensor such as an accelerometer for detecting a state of a magnetic head or a support for the magnetic head at a period shorter than a sampling period of the servo signals. Since an accelerometer mounted on the magnetic head or the support for the magnetic head detects an acceleration, the control performance of a servo control system can be improved, such as reduction of generation of mechanism resonance vibrations of a carriage and improvement on detection precision of a speed signal.

Abstract: A disc drive includes a transducer having a separate element for writing information and a separate element for reading information to and from the disc. In a disc drive designated to read and write long sequential records, the track misregistration budget is reduced to account for previously written tracks not being encroached on one side. An initial track is written. Subsequent tracks are written after a seek in one direction. The subsequent track is written so that the initially written track is overwritten to one side and leaves a track having a width substantially equal to the width of the read element. Records can be written into data bands of a selected number of tracks. A guard band is left between groups of data bands so that data on tracks in subsequent data bands are not overwritten.

Abstract: A magnetic disc storage apparatus including a magnetic head for reading information from a storage track on a magnetic storage disc driven to spin, a voice coil motor for moving the magnetic head above the disc, and a magnetic head drive system for executing a position control of the magnetic head by controlling driving current of the voice coil motor by a feedback control while monitoring a state of reading the magnetic head in which the magnetic head drive system includes multi-mode driving means for executing a linear drive mode for controlling, as an analog amount, the driving current of the voice coil motor when an amount of driving to move the magnetic head is small and executing a pulse drive mode for controlling, as a digital amount, the driving current of the voice coil motor when the amount of driving to move the magnetic head is large.

Abstract: With respect to the disk drives provided power from a single power source in a disk drive system, start up power is first supplied to a first start-up group of the disks, preferably comprising all of the master disks, with the size of the group being selected so that the required current does not exceed the capacity of the power source. When the disk drives of the first group have substantially reached steady state, start-up is conducted with respect to a second start-up group of the disk drives so that the current required during start-up for the second group and the current required for steady state drive of the first start-up group does not exceed the capacity of the power source. With respect to each start-up group, the number of disk drives is the maximum integer value and decreases or remains the same with respect to subsequent start-up groups.

Abstract: An apparatus and method for minimizing audible noise in disc drives during idle periods uses a low-noise velocity profile and/or low noise position profile to govern the movement of a seeking actuator assembly. The low-noise velocity profile is selected to govern all actuator movement and seeking during idle periods, i.e., during internal drive housekeeping operations. The noise level associated with each actuator position in the drive is preferably determined through actual tests and/or modeling and is utilized to determine the low noise profiles. The relative amount of time the actuator assembly spends in the relatively noisier actuator assembly positions may also be optimally reduced thus reducing the overall amount of noise generated by an idle disc drive.

Abstract: The present invention provides a method and storage device for reducing the occurrence of data miscompare errors. The method includes identifying a destination track as either an even track or an odd track and selecting a pseudo-random set of data based on this identification. The pseudo-random set of data is combined with write data to produce randomized data that is used as the basis for a write signal to be written to the destination track.

Abstract: A disc drive with an information portion previously written on a rotatable disc surface, a servo write clock generator phase lock loop circuit controlling timing for writing a reference mark to the rotatable disc surface in substantial time alignment and phase and frequency coherent with the information portion previously written to the rotatable disc surface, a servo write clock generator phase lock loop circuit controlling timing for writing the reference mark, a pulse detector circuit for creating logic level signals from the reference mark, a pattern generator for generating reference mark write signals from the logic level signals, a memory buffer for storing radial position correction tables and values for writing the reference mark, and a self-servo control and sequencing circuit synchronizing timing signals for writing the reference mark to rotatable disc surface of disc drive.

Abstract: The present invention is directed to a disk drive that employs a proximity recording interface in which a slider that carries a head is designed to remain in contact with the disk during data transfer operations to achieve a high data density. In particular, the present invention is directed to cleaning debris from a pad on the slider that carries the head. The debris, if allowed to accumulate, can reach a depth at which the head is spaced from the disk at a distance which adversely affects the transfer of data with the disk. In one embodiment, the spin motor of the disk drive is caused to rotate at a lower angular velocity than during normal data transfer operations, preferably using open loop control, while the actuator of the disk drive is used to radially displace the slider and associated head, also preferably using open loop control. For a constant angular velocity of the disk, the change in radial position causes different areas of the pad to be contacted and cleaned by the disk.

Abstract: A voice coil motor control circuit provides control signals to a voice coil motor circuit drivel that is coupled to a voice coil motor. A current sensing resistor is coupled in series with the voice coil motor. The control circuit includes a sense amplifier having inputs that couple to the current sensing resistor and includes a feedback circuit that includes an input and also includes an output that couples to the voice coil motor driver. In a first mode of operation, the feedback circuit input is coupled to an output of the sense amplifier. The control circuit also includes an inverting operational amplifier. In the first mode of operation, the inverting operational amplifier is bypassed. In a second mode of operation corresponding to deployment of a read/write head from a parked position onto the disc, the inverting operational amplifier is coupled in series between the sense amplifier output and the feedback circuit input.

Abstract: A recording disk apparatus is provided. The recording disk apparatus includes a recording disk having at least one recording surface with a plurality of spaced recording tracks. The recording disk also includes a positioning arm with a head assembly. The head assembly has a plurality of read transducers. Each consecutive transducer is positioned relative to one another at a distance substantially smaller than a spacing between two consecutive tracks.

Abstract: A method for controlling the current applied to a voice coil motor (VCM) prevents overheating of a coil in the VCM. The method includes the steps of defining an acceleration interval for measuring the distance traveled by a head moved by the VCM. The method also defines a distance traveled during the acceleration interval which can be used as a reference for indicating that the coil is being overheated. The VCM is driven for the acceleration interval and the distance traveled during the interval is measured and compared to the reference distance. If the difference exceeds a threshold, then the current being applied to the coil is controlled to maintain the coil temperature within a limit. If, however, the difference does not exceed the threshold, the current being applied to the coil is controlled to meet a performance requirement.

Abstract: An apparatus and method for evaluating surface characteristics of a recording disc prior to incorporation into a disc drive. A glide test system includes a glide test head supportable over the disc, the glide test head having a negative-pressure air bearing slider and a contact sensor which outputs a signal when the glide test head contacts a feature of the disc surface. The glide test head and the disc are characterized as opposing plates of a variable capacitor with a dielectric layer therebetween including at least a layer of air supporting the glide test head. A voltage source, operably coupled to the glide test head and the disc, applies a fly height control voltage across the capacitor to adjust the fly height of the glide test head. The disc surface preferably comprises a data region configured to magnetically store data as the disc is rotated and a texturized landing zone configured to support the disc drive read/write head when the disc is stopped.

Abstract: A disc drive including rotatable disc surface adjacent a positionable read/write head having a write element offset from a read element in one direction across the rotatable disc surface from an outer diameter of the disc surface to an inner diameter of the disc surface for writing head position control fields by steps for controlling writing of second head position control fields on a second portion of the disc surface while reading head position control fields written on a first portion of the disc surface, using the read element, to augment position-control of the write element being controlled by a position information writing apparatus, while writing the second head position control field to the second portion of the disc surface.

Abstract: A seek pattern formation circuit includes a seek pattern generation circuit for generating a seek pattern formed of a predetermined pulse train every time a step pulse is applied and a seek pattern shaping circuit for shaping the seek pattern and supplying the shaped seek pattern to a stepping motor driver. When the period for which the step pulse is supplied is shorter than the period for which the seek pattern is generated, and when at least one of pulses included in the seek pattern is very narrow, the seek pattern shaping circuit selectively eliminates the narrow pulse. As a result, narrow pulses which may induce noise are not supplied to the stepping motor driver, and hence a malfunction in the stepping motor driver does not occur.

Abstract: Apparatus and method for compensating for servo data distortion in a disc drive. During a seek wherein a head is moved from an initial track to a destination track on a disc surface, servo position data are decoded on intermediary tracks by generating nominally redundant positive and negative digital pulse streams from positive and negative peaks in a servo readback signal. The positive and negative digital pulse streams are combined using a default Boolean logical operator (such as an AND operator) to qualify pulses in a first output digital pulse stream used to determine head position. When distortion arises that prevents correct detection of head position from the first output digital pulse stream, a second Boolean logical operator (such as an OR operator) is switched in to generate a second output digital pulse stream. Depending on the type of distortion, a selected one of the operators will provide improved servo data decoding.

Abstract: A method and apparatus to determine and correct track spacing during self-servowriting on a rotating recording medium. The recording medium comprising a plurality of tracks, wherein each track comprises a plurality of sectors, and a transducer mounted on an actuator arm pivotally coupled to a voice coil motor (VCM). The actuator arm is positioned by a servo. The method comprising the steps of: servowriting the at least one of the plurality of sectors with a servo pattern consisting of recorded transitions. The servowriting is performed on one more tracks within the sectors where the number of tracks being servowritten is less than total number of tracks that fills the rotating medium. The transducer is positioned relative to the rotating recording medium to a preselected radial position over a previously servowritten area of the rotating recording medium that has one or more previously recorded transitions.

Abstract: A method and system for reducing positioning noise in a data storage system are provided. An access device is positioned over a data storage medium using a stream of bursts stored on the medium. The bursts are sensed at a frequency determined by the rate at which the medium is moved relative to a sensing device. Output positioning values are provided to position the access device at a frequency higher than the frequency at which the positioning bursts are sensed, and/or at random times. The random times may be calculated as random advances or delays from time points occurring at a fixed frequency.

Abstract: A disk drive recording apparatus includes an actuator arm with first and second heads extending from the actuator arm for writing and reading data to and from a first surface of a disk recording medium The first and second heads are spaced apart from each other in a circumferential direction along the first surface of the disk recording medium. A switching device switches a data input/output path between the first head and the second head in response to a control signal. A microprocessor identifies a target position on the first surface of the disk recording medium and determines which one of the first and second heads is closer to the target position. The microprocessor then generates the control signal to switch the data input/output path to the first head when the first head is closer to the target position, and generates the control signal to switch the data input/output path to the second head when the second head is closer to the target position.

Abstract: A significant change in the static angular position can be produced from a small physical displacement of the flexible member. The flexible member 12 in a magnetic head unit 95 is stressed for adjusting the static angular position. Simultaneously, the stressed areas 14 are irradiated by a laser beam LA.

Abstract: A sector servo type magnetic disk apparatus is provided with, in addition to servo signals, a sensor such as an accelerometer for detecting a state of a magnetic head or a support for the magnetic head at a period shorter than a sampling period of the servo signals. Since an accelerometer mounted on the magnetic head or the support for the magnetic head detects an acceleration, the control performance of a servo control system can be improved, such as reduction of generation of mechanism resonance vibrations of a carriage and improvement on detection precision of a speed signal.

Abstract: In a servo area SA on an empty track outside a user data read/write area to and from which a user data of a floppy disc is written and read, a format information FI of the floppy disc is recorded. The format information FI is recorded along with a track number TN in a gray code area GA in the servo area SA. Thereby, the format of the floppy disc can be identified with no identification hole or the like formed in an envelope encasing the floppy disc.

Abstract: A system for controlling movement of a head over tracks on a disc in a disc drive includes a servo positioner for positioning the head over a desired track, a sectoring circuit for determining when the head is over a data sector on the desired track, a formatter for controlling data transfers to and from the desired track, and a controller for providing the servo positioner with a track address indicative of the desired track. A track change system is coupled to the formatter and the servo positioner, and provides a direct communication channel between the servo positioner and the formatter. Thus, the data transfer can be carried out utilizing communications between the formatter and the servo positioner, without waiting for the microcontroller to be interrupted.

Abstract: An information storage apparatus has a disk medium setting data recording areas along a plurality of tracks concentrically arranged, a head for recording and reproducing data on tracks of the disk medium, an actuator for moving the head to a desired track among the plurality of tracks. Also included is an electric circuit for controlling recording and reproducing in response to detecting the distance from a recorded magnetization pattern on an adjacent track in the radial direction by detecting previously recorded signals on adjacent tracks while data recording. Even if the track density is increased, the upper limit of a threshold value of a function for preventing off-track recording of the information storage apparatus can be increased and a high track density of the information storage apparatus can be easily realized.

Abstract: A method and system for determining data sector splits across servo bursts in a disc drive having a data disc with an embedded servo configuration. The disc drive includes a data transducer selectively positionable over the data disc for transferring data to and from the data disc, and the data disc includes a plurality of zones of predefined tracks. The method includes locating one or more frame table parameters based on a new zone position, creating a plurality of new frame table entries, while the disc drive is in operation, based on the frame table parameters, and moving the data transducer from a past zone position to the new zone position. The disc drive includes parameter memory and frame table memory. The parameter memory contains a plurality of zone records, with the zone records containing a plurality of zone table parameters. The frame table memory is utilized to store a frame table.

Abstract: A read/write head servo control system for data recording devices, wherein a method of compensating initial values is utilized to generate a control signal to move the head from an initial position to a target position. The method estimates and stores multiple position compensation values. A first control signal moves the head from an initial position to a target position. Head position values are sampled as the head moves. Head position deviation values are calculated for the sampled position values. The head position values are utilized to select a set of estimated position compensation values. These values are in turn utilized to generate a second control signal, which is then utilized to control the position of the head.

Abstract: A removable magnetic cartridge provides enhanced data access. The removable magnetic cartridge includes a rigid casing, and a magnetic disk disposed within the rigid casing. The magnetic disk includes a top surface for storage of data, and a bottom surface for storage of data, the bottom surface including at least a first cylinder and a second cylinder, the second cylinder adjacent the first cylinder, the first cylinder having a first plurality of logically numbered servo bursts including a reference servo burst and a secondary servo burst, the secondary servo burst positioned at an angular displacement relative to the reference servo burst, the second cylinder having a second plurality of logically numbered servo bursts including a reference servo burst located at approximately the angular displacement relative to the reference servo burst of the first cylinder.

Abstract: a hard disk drive system (10) includes a rotating magnetic disk (16), and a support arm (22) which is supported for movement relative to the disk under control of a voice coil motor (21). a microactuator (26) supports a read/write head (27) on the support arm for movement relative thereto. a control arrangement (13) controls the voice coil motor and the microactuator in response to position information (31), which is read by the read/write head from the disk and which indicates the position of the read/write head relative to the disk. The system is free of a sensor for detecting the actual position of the support arm relative to the read/write head or the disk.

Abstract: A capacitor powered electronic emergency device retracts and parks an actuator into a resistive parking position with a crash stop barrier. Due to variations of the kinetic status of the actuator at the begin of the retraction, the actuator reaches the resistive parking position with different velocities, which can be at a level that causes the actuator to bounce off the crash stop barrier. A modulating pulsing of the energy flow extends the discharge time of the capacitor long enough to provide sufficient energy to compensate an eventual bounce-off. The use of transistors in the device keeps the internal energy consumption low. An increase of the pulsing frequency in dependence on the capacitor voltage results in a high average current flow.

Abstract: A first clock track is written to a data storage region of a storage medium at a first position between first and second boundaries. A first set of further clock tracks is written to other positions on the data storage region, these other positions lying between the first position and the first boundary. A second set of further clock tracks is written to other positions on the data storage region, these second other positions lying between the first position and the second boundary.

Abstract: After data recording or reproduction is finished, servo control is stopped within a predetermined time to disable a positional compensation output to a head. While servo control is being stopped, servo data recorded in a medium is monitored. When the head is moved on the medium further than a predetermined distance, servo control is activated to start a positional compensation output to the head. The stop/start of the servo control is implemented by software embedded in the CPU of a disk apparatus.

Abstract: The method of the present invention is capable of shortening the time required for positioning an inner actuator and writing servo track signals on a magnetic disc, and improving the quality of the written servo track signals. The amount of displacement between the inner actuator and an external actuator is detected with a present position of the external actuator. A first deviation between a travel destination of the external actuator and a present position of the inner actuator is detected on the basis of the amount of the displacement, the present position of the external actuator and the travel destination thereof. The inner actuator is controlled so as to make the first deviation within a predetermined standard range.

Abstract: In a ultra high density, multiple-disk drive, track switches within a cylinder of tracks as well as track switches to tracks on other cylinders both require a movement of the head stack actuator. Track switching latency in such a disk drive is reduced by overlapping pre-movement portions of the track switching process with the data transfer operation of the currently active recording head. In addition, post-movement portions of the track switching process are overlapped with the movement of the heads so that the next selected read/write head may begin a data transfer operation immediately upon arrival at the next track. Further, the pre-movement and post-movement portions of the track-switch process may be overlapped with low displacement movement of the read/write heads relative to the currently active track or the next track.

Abstract: A preferred system for measuring bearing friction first measures voice coil motor current values required to move an actuator arm assembly to each of several cylinder position intervals. Torque values required to move the actuator arm assembly are then computed using the measured voice coil motor currents. Drive-level bearing friction values are then calculated using the computed torque values and then combined into a composite indicator.

Abstract: A skip mask mechanism is implemented in a disc drive in order to increase performance by minimizing the number of necessary disc rotations required while executing a set of pseudo-sequential commands. The drive includes an interface between the host computer and the drive, a read/write channel between the interface and the transducer/head, a formatter between the interface and the read/write channel for timing when data is transferred between the interface and the read/write channel, and a skip mask mechanism interposed between a target calculator and the formatter that provides a masked input to the formatter for controlling passage of data between the interface and the read/write channel.

Abstract: A controller for read/write head actuator of a hard disk drive system includes a feedback unit providing a voltage to a servo-actuator motor. The feedback unit includes a first fuzzy logic rule-based algorithm unit for the seek mode and a second fuzzy rule-based algorithm unit for the track mode. In the seek mode, the first algorithm unit, based on present position and delta (velocity) parameters, determines an optimum velocity. A signal representing the optimum velocity is compared with a signal representing the present velocity and an appropriate signals applied to the head actuator unit. The use of the fuzzy logic rule-based algorithm permits a near-minimum seek time even in the presence of non-linear and varying parameters. The output signal from the seek mode apparatus or the output signal from the track mode apparatus is selected based on position and velocity parameters.

Abstract: In a magnetic recording apparatus including a support arm movable with respect to a magnetic recording disk, a first actuator for moving the support arm with respect to the magnetic recording disk, a pair of support members at least one of which holds a magnetic head thereon and each of which is connected to the first actuator through the support arm to be driven by the first actuator through the support arm, and a pair of second actuators for moving respectively the support members with respect to the support arm so that the support members are respectively moved with respect to the magnetic recording disk by the first actuator and the second actuators, the second actuators move simultaneously the support members respectively with respect to the support arm in respective directions opposite to each other.

Abstract: This invention relates to head position control method for a disk device the uses a disk medium whose tracks have been formatted externally, and the disk device that effectively uses the range of motion of an actuator. In a disk device that has a disk medium (2), head (3), actuator (5), a control circuit (8), there is a conversion mechanism (31) that sets a data area in the writing range of the disk (2) that corresponds to the range of motion of the actuator, and converts a logical address to a physical address in the data area. This invention makes it possible to set a storage capacity that makes maximum use of the range of motion of the actuator for any device, even when there is position offset in the range of motion of the actuator.

Abstract: A data recording and/or reproducing apparatus which scans a head over a disc on which a servo pattern for moving the head to a predetermined position is recorded in an arc forming a part of a concentric circle. The apparatus comprises a track No. detector and fine signal detector, for detection of the servo pattern, a circumferential position detector to detect a circumferential position on the disc, an offset calculator to calculate an offset of a current position on the disc from the detected circumferential position, and a positional difference calculator. The calculated offset of the current position is added to the positioning signal to control the head scanning orbit on the disc to be spiral.

Abstract: With respect to the disk drives provided power from a single power source in a disk drive system, start up power is first supplied to a first start-up group of the disks, preferably comprising all of the master disks, with the size of the group being selected so that the required current does not exceed the capacity of the power source. When the disk drives of the first group have substantially reached steady state, start-up is conducted with respect to a second start-up group of the disk drives so that the current required during start-up for the second group and the current required for steady state drive of the first start-up group does not exceed the capacity of the power source. With respect to each start-up group, the number of disk drives is the maximum integer value and decreases or remains the same with respect to subsequent start-up groups.

Abstract: An apparatus for providing sector location pulses to a controller of a rotating disk data storage device having a counter clocked in proportion to the disk rotation rate and an accumulator for accumulating times to sectors on the disk. A comparator connected to the counter and the accumulator enables an accumulator clock for repetitive clocking of the accumulator at such times the contents of the accumulator do not exceed the contents of the counter. A sector location pulse generator connected to the comparator generates the controller pulses, when enabled, concurrently with the accumulator clock signals. A master reset generator resets the first counter and the accumulator each time an index location on the disk passes a transducer head used to read and write data to and from the disk and a partial reset generator resets the accumulator each time the transducer head is moved between tracks on the disk.