Abstract: A magnetic characteristic inspecting apparatus including a plurality of disk rotating devices or a plurality of magnetic heads include a unit for switching output signals of write signal production units or allocating the output signals to the magnetic heads, a unit for switching signals read from the magnetic heads or allocating the read signals to measurement resources, and a unit for selecting any of the disk rotating devices synchronously with which the measurement resources will perform measurement. The write signal production units and measurement resources are shared among inspections of the plurality of disk rotating devices or the plurality of heads.

Abstract: A head holder includes a first and second blocks connected each other with a predetermined gap between the blocks by a flexible coupling portion. The second block supports the first block swingably by increasing a width of either one of spaces of the predetermined gap on opposite sides of the coupling portion and narrowing the other space by bending the coupling portion by a piezo actuator. A magnetic head is dynamically moved in a direction crossing a track by swinging a head assembly fixed to the first block.

Abstract: The perpendicular magnetic head fabrication and testing method includes the additional fabrication of magnetic pole testing structures in the kerf area of the wafer substrate. Particularly, magnetic interconnect pieces are fabricated in the kerf area to magnetically connect an extending portion of the first magnetic pole with an extending portion of the second magnetic pole. As a result, when the perpendicular magnetic heads are fabricated at the wafer level, the first and second magnetic poles are interconnected through structures located in the kerf area. Thereafter, an ISAT magnetic pole test can be conducted by passing electrical current through the induction coil of the magnetic head, and magnetic flux will flow through the interconnected magnetic pole structure, thereby enabling the testing of the magnetic poles of the perpendicular magnetic head at the wafer level.

Abstract: A method for testing electromagnetic characteristics of magnetic media while maintaining consistent performance of a read/write head and recording channel is disclosed. The disclosed method is performed such that reduced statistical sampling is achieved. The method includes recording a first set of baseline measurements utilizing a first magnetic media with the read/write head and recording channel. The first magnetic media is then removed from an assembly containing the read/write head and recording channel and is replaced with a second magnetic media. Measurements are made utilizing the second magnetic media with the read/write head and recording channel, wherein the measurements are comparable with the baseline measurements and wherein consistent performance of the read/write head and the recording channel is maintained so as to reduce the size of statistical samples needed.

Abstract: A lifecycle analyzer includes a temperature control element for controlling the temperature of a plurality of magnetoresistive (MR) elements, which may be, e.g., in bar, slider, head gimbal assembly, or head stack assembly form. The MR elements are in electrical contact with a stress probe element for applying a bias voltage or current stress. The MR elements and/or a magnetic field generator are moved to place one or more MR elements within the magnetic field of the magnetic field generator for testing. During testing, the MR elements are in electrical contact with a test probe element. The temperature of the MR elements may be controlled during both the stressing and testing.

Abstract: A device and method for testing a slider of a head-gimbal assembly during disc drive manufacturing. The device includes a test disc, an actuator arm and a control module. The test disc has a first circumferential area for detecting contact between the slider and the test disc and a second circumferential area for burnishing sliders that contact the first circumferential area as the test disc rotates at or above the predetermined velocity. The head-gimbal assembly is affixed to a support, or flexure, on the actuator arm such that the slider is operable to move between an inner diameter and an outer diameter of the test disc. The control module controls rotation of the test disc and movement of the actuator arm, and thus the slider, relative to the test disc. The control module monitors the slider-disc interface for contact therebetween. If contact is detected, the slider is either burnished or the head-gimbal assembly is discarded altogether.

Abstract: A testing method for a magnetic hard disk or a magnetic head in a test system includes a moving step in which the magnetic head, which moves to fly closely over the magnetic disk, moves to a predetermined radial position corresponding to the position data of the magnetic disk which rotates at a predetermined constant speed; a reading step in which imbedded position data is read out for each sector of the magnetic disk is by the magnetic head; and a reading/writing step in which a predetermined signal is written in or read out from a data area of the sector by the magnetic head when the position data is one of equal to a predetermined value and within a predetermined range.

Abstract: The magnetic head tester of the present invention drives a medium for rotation to float a slider from the medium so as to test a magnetic head for its characteristics, and the tester includes a holder removably holding the slider opposed to the surface of the medium, and suspension means provided in the holder which has the same function as a suspension supporting the slider in a real apparatus. With this tester, tests can be executed by exchanging the slider alone, and it is unnecessary to discard the suspension even when the magnetic head is judged to be defective, thus the loss of production costs for the suspension and processing costs for assembling the slider in the suspension can be avoided.

Abstract: An electrical property evaluation apparatus for measuring an electrical property of an object includes a magnetic field generating mechanism that generates a magnetic field in a target area on the object, and a magnetic sensor for measuring the magnetic field near the target area. A cantilever having a conducting probe is supported so that the probe can be brought into contact with the target area. A bending measurement mechanism measures an amount of bending of the cantilever when the probe is brought into contact with the object. A control section controls a moving mechanism to maintain the bending amount of the cantilever constant. A voltage source applies a voltage to the probe, and an electrical property measuring section measures a current or an electrical resistance between the probe and the object in contact with each other.

Abstract: A DC current is supplied to the write coil of a GMR head 1 equipped with a completed HGA (Head Gimbal Assembly). The element part of the GMR head 1 is thereby thermally deformed. Thus deformed, the element part protrudes, abutting on a rotating laser-bump disk 2, above which the HGA is floating. When the element part abuts on the disk 2, a magnetic field (2470 gauss) that extends in a direction opposite to the magnetization direction of the fixed layer of the GMR head 1 is applied to the top of a core slider 5.

Abstract: A method and system for testing a plurality of RFID devices disposed on a common carrier. In one embodiment, the RFID devices are evenly spaced along the length of the carrier, and the system comprises a short-range tester, a long-range tester and a computer, the short-range tester being coupled to the computer and having a short-range testing position, the long-range tester being coupled to the computer and having a long-range testing position, the long-range testing position being spaced downstream from the short-range testing position by a known number of device positions. In use, an RFID device of interest is first positioned at the short-range testing position, and the short-range tester reads a unique identifier for that RFID device and communicates the identifier to the computer. The carrier is then advanced so that subsequent RFID devices are read by the short-range tester.

Abstract: A method is disclosed for testing pinned layers of magnetic disk drive read heads having at least one pinned layer, where the magnetic orientation of the pinned layers has been set in an initial direction. The method includes applying a large magnetic test field at a reverse canted reset angle. First test responses from the disk drive read heads are then measured in a small magnetic test field. A large magnetic test field is applied at normal canted reset angle. The disk drive heads are then subjected to a full suite of performance tests in a small magnetic test field to verify their acceptability. These second test responses are then compared to the first test responses to identify read heads having weakly pinned layers.

Abstract: Pressing means is provided to press a movable base to a surface of a reference base to make the movable base in contact with the surface of the reference base to thereby lock-down the movable base on the surface of the reference base. The movable base is moved while slightly floating with respect to the reference base. A movable floating mechanism is provided to float the movable base from the reference base against pressing force of the pressing means exerted on the movable base to thereby relieve the locking. A floating amount of the movable base from the reference base may be small enough to reduce or substantially remove sliding friction between the movable base and the reference base. For example, the floating amount may be as small as ten to several hundreds microns.

Abstract: An XY stage includes a movable frame having a rectangular space inside thereof and movable on a reference base along one of X and Y axes, a first drive source provided in the reference base for moving the movable frame, a rectangular movable base mounted in the rectangular space of the movable frame, which is movable on the reference base along the other of the X and Y axes and stopped on the reference base, and a second drive source provided in the movable frame, for moving the movable base.

Abstract: A spin stand testing system is used to determine a positioning range of a microactuator disposed on a head gimbal assembly. The microactuator is configured to laterally translate a read sensor of a head of the head gimbal assembly through the positioning range. The spin stand testing system includes a disk having a track, and a secondary mover configured to laterally translate the head gimbal assembly. During testing, a feedback loop keeps the read sensor locked to the track. While the read sensor remains locked, the head gimbal assembly is translated laterally. The microactuator translates the read sensor in an opposite direction until the microactuator reaches an end of its range, which is determined by monitoring a signal. The amount of translation of the head gimbal assembly by the secondary mover when the signal indicates the end of the range is the measured positioning range in one direction.

Abstract: A method for measuring a magnetic read width MRW of a magnetic read sensor directly from the derivative of a full track profile, with better accuracy and more advantages than the micro-track method was invented and also there is no need to use a separate wide write head. The magnetic write width MWW of the write head, without the influence of sensor side reading, can also be obtained by this method along with the MRW with no additional calculations.

Abstract: A testing method for a magnetic hard disk or a magnetic head in a test system includes a moving step in which the magnetic head, which moves to fly closely over the magnetic disk, moves to a predetermined radial position corresponding to the position data of the magnetic disk which rotates at a predetermined constant speed; a reading step in which imbedded position data is read out for each sector of the magnetic disk is by the magnetic head; and a reading/writing step in which a predetermined signal is written in or read out from a data area of the sector by the magnetic head when the position data is one of equal to a predetermined value and within a predetermined range.

Abstract: A write precompensation amount setting method and apparatus comprise a function detecting the respective head characteristics with an electric current used at an ordinary temperature and a irregular electric current, and a function setting an optimum write precompensation amount at a low temperature according to the detected head characteristics. As a result, a write precompensation amount is corrected according to the characteristics of the normal current and the irregular current, and a write precompensation amount is determined, so that the write precompensation amount with higher accuracy than that with a conventional technique can be determined.

Abstract: In the method of inspecting a thin-film magnetic head, a thin-film magnetic head provided with a magnetoresistive film having a free layer whose magnetization direction changes depending on an external magnetic field and ferromagnetic layers for applying a bias magnetic field to the free layer is prepared. Then, a DC magnetic field is applied to the ferromagnetic layers in the bias magnetic field applying direction. Subsequently, an AC magnetic field is applied to the ferromagnetic layers in the bias magnetic field applying direction. Thereafter, an external magnetic field is applied to the magnetoresistive film while supplying a current thereto, and a property of the thin-film magnetic head such as asymmetry and reproducing output is inspected.

Abstract: An asynchronous system for testing disk drives includes a test platform that includes a plurality of slots for receiving and for providing communication with drives. The slots are segregated into a plurality of groups configured to satisfy predetermined environmental, communication bandwidth and test schedule requirements of the drives to be loaded therein. An automated loader/unloader is configured to selectively load drives into and out of the platform and to move drives between the plurality of groups. A module controller is assigned to each group of slots, each module controller being coupled to the slots of its assigned group and configured to administer at least one test to drives loaded in its assigned group while insuring that the predetermined environmental, communication bandwidth and test schedule requirements of its assigned group remain satisfied.

Abstract: A method for identifying a problem with a magnetic disk, comprising testing both sides of a disk for read errors using a pair of heads, flipping the disk 180 degrees, again testing both sides of the disk for read errors using the same heads, determining whether one side of the disk has more errors than the other side both before and after the flip, and determining that the disk is the cause of the read errors if the same side of the disk still has more errors than the other side after the flip.

Abstract: A magnetic head and disk tester comprises a base, a spindle for rotationally supporting a magnetic disk, a carriage for supporting a magnetic head support which carries a magnetic head with a magnetic read/write element, and a dual-stage positioning system that moves the carriage in two perpendicular directions X and Y. The magnetic head support, the magnetic head and the magnetic read/write element have a common longitudinal axis Z. The head support is positioned such that the longitudinal axis Z forms a predetermined angle between 0° and 90° with respect to the Y direction. Preferably the predetermined angle is about 45 degrees. When the head is driven from one point of an inner track to a point of an outer track, the displacement of the head along X axis is relatively large and the displacement of the head along Y axis is relatively small.

Abstract: This invention relates to a testing method for a head IC which makes it possible to simplify checking of the head. The head IC is installed on a head suspension, and probes are placed on terminals of the head suspension to check electric characteristics of the head IC. With this invention, contact of the probes for checking the head IC when the head IC has been installed, but before installing the head, becomes easier.

Abstract: A device for handling and testing individual sliders in a row-like format utilizes an elongated, row-like holder having a series of small pockets, each of which receives a single slider. After the sliders enter the holder, a clamp is moved to a closed position to retain the sliders in the holder. The holder is placed in a test fixture such that permanently mounted probes precisely engage the small pads on the sliders for multiple testing purposes. Enlarged probe pads on the test fixture are electrically interconnected with the probes to provide an operator with easy access to the slider pads. The sliders are tested in a row-like format, side by side, to reduce handling-induced electrostatic discharge and mechanical damage.

Abstract: An object is to automatically detect the positions of spike noise, create a distribution diagram, and perform pass/fail decisions. The cross-correlation function of the signal waveform from a magnetic head 1 and a reference waveform simulating spike noise is used in extraction of spike noise. The number of peaks in the cross-correlation function exceeding a threshold value is counted, and quantitative evaluation of spike noise is performed.

Abstract: A novel magnetic imaging microscope test system with high spatial (1–10 nm) and temporal (˜1 ns) resolution of the magnetic field is disclosed, as well as the system application for characterization of read and write heads for magnetic recording. The test system includes a scanner assembly and a work piece holder for holding a work piece to be tested. The scanner assembly and the work piece holder are positionable relative to each other at very fine resolution during scanning. A probe arm is cantilevered from the scanner assembly to bring a probe head into close proximity to the work piece holder. The probe head is configured scan a work piece in contacting engagement therewith so that a magnetic device on the probe head magnetically interacts with a magnetic field generating or magnetic field sensing device on the work piece. A probe head for use in the test system and a related test method are also disclosed.

Abstract: A method of connecting a plurality of probe pins to a plurality of first external connection pads, which are provided on a head gimbal assembly and are electrically connected to a plurality of terminal electrodes of a write magnetic head element, respectively, and a plurality of second external connection pads, which are provided on the head gimbal assembly and are electrically connected to a plurality of terminal electrodes of a read magnetic head element. In the connection method, an approach direction of the probe pins to the first external connection pads and an approach direction of the probe pins to the second external connection pads are made different from each other.

Abstract: The invention relates to a method for characterizing a ferroelectric material, comprising application of an electric voltage to a sample of said ferroelectric material, measuring the electric current flowing through said sample, and joint treatment of the applied voltage signal and the measured current signal in order to provide representation data characterizing the polarization of the ferroelectric material. The method also includes controlling the applied electric voltage in such a way that superpositioning can be performed for a first current component having a large signal amplitude at a first frequency and a second current component having a second small signal amplitude at a second frequency which is much greater than the first frequency, and identifying the characteristics of the ferromagnetic material respectively associated with locally reversible polarization effects and locally irreversible polarization effects.

Abstract: A method is described for calculating head disk interference (HDI) using a dynamic parametric test. In one embodiment, HDI is calculated based on an actual and ideal sensitivity profile based on a read-back signal track profile for the slider/head.

Abstract: A method of testing a performance of the HGA has a step of writing information from the at least one thin-film magnetic head element onto a magnetic disk with driving the actuator for displacement by applying an alternating drive signal to the actuator, a step of reading out the information of at least one rotation of the magnetic disk by the at least one thin-film magnetic head element without driving the actuator for displacement, a step of storing the information read-out from the magnetic disk as a read-out information along a disk-rotating direction, a step of moving the HGA toward an off-track direction by a predetermined distance, a step of repeatedly executing the reading, storing and moving steps to obtain two-dimensional read-out information along the disk-rotating direction and the off-track direction, and a step of determining, from the two-dimensional read-out information, an off-track position where the read-out information becomes maximum at each position along the disk-rotating direction, the

Abstract: A method and apparatus for detecting a high flying condition of a transducer head in a computer disk drive is provided. The method and apparatus allow the detection of high fly write events that occur over one or a small number of data sectors. In addition, the present invention provides a method and apparatus for detecting high fly write events with a great deal of sensitivity. The method and apparatus of the present invention provide quick response and high sensitivity by monitoring the strength of a signal derived from data written to the disk, and signaling a high fly write event if the monitored signal strength in connection with a particular piece of data is less than a stored high fly write number corresponding to that piece of data by a predetermined amount.

Abstract: A method characterizes a generally-trapezoidally-shaped portion of a writing pole of a perpendicular magnetic write head in proximity to a magnetic medium. The method includes providing measured track width data corresponding to magnetic track widths of a plurality of tracks written by the writing pole on a rotating magnetic medium underlying the writing pole. The magnetic track widths vary as a function of skew angle of the writing pole during writing. The method further includes determining a magnetic width of the wider of a leading edge and a trailing edge of the writing pole from a first portion of the measured track width data corresponding to a first range of skew angles. The method further includes determining at least one magnetic taper angle of the writing pole from the measured track width data.

Abstract: A method is provided for testing a magnetoresistive sensor for polarity reversal. In one embodiment, the method includes: writing a test pattern on a magnetic disk; providing a mechanical or thermal stress to the magnetoresistive sensor for a period of time; and, comparing the polarity of the test pattern before and after the application of stress.

Abstract: Disclosed is an apparatus and method for dynamic fly height and roll adjustment of a physical asperity sensor (PAS) head. The PAS head is used to test disk asperity heights and mechanical interference (commonly known as glide height and take off height). The PAS may be adjusted through a pivoting device such as a joystick coupled through one or more actuators to the pivoting device by actuator arms. In one embodiment, the actuator is a piezoelectric motor. The PAS head may utilize a detector to indicate the distance of the disk asperity from the PAS head. The method comprises receiving the signal and in response, operating the actuators to adjust the position of the pivoting device to obtain a selected positioning of either the fly height or the roll of the PAS.

Abstract: A magnetic head that includes a magnetoresistive effect read head element is tested by applying a varying magnetic field and measuring the resulting output signals from the read head element. The output signals are digitized and a processor calculates, e.g., the root mean square (RMS) of the signals or performs a Fast Fourier Transform or Autocorrelation on the data to determine if there is noise present. If desired, write and delay events may be performed prior to digitizing the output signals from the read head element to determine if additional noise, which is introduced to the magnetoresistive head from the write element, is present. In one embodiment, the digitizer may be replaced with an RMS meter.

Abstract: A system and method for evaluating a device under test (DUT) that utilizes a model of the DUT interfaced to DUT interface logic, which is designed to interface the DUT to automated testing equipment (ATE). By ensuring that the model includes a description of the DUT and of the DUT testing interface, conditions such as connections between ports of the IC (i.e., buddying) that may or may not be interfaced to the ATE may be included in the model to enable precise test pattern sets to be generated using the model. The test pattern sets may be used by a simulator to test the design of an IC or by ATE to test a fabricated IC having the design.

Abstract: A lifecycle analyzer includes a heating element for heating a plurality of magnetoresistive (MR) elements, which maybe, e.g., in bar form. At one location the MR elements are in contact with a stress probe card for applying a bias voltage or current stress. The MR elements are moved to a separate location, where there is a test probe card and magnetic field generator for testing the MR elements after being stressed. In one embodiment, a subset of the plurality of MR elements is tested at a time. The lifecycle analyzer includes an in-situ abrasive element that is used to abrade the probe pins of the stress probe card to remove oxidation that results from extended contact with the heated MR elements.

Abstract: A method and apparatus produce a read signal using a read head. A variable gain value is set that is used by a variable gain amplifier to amplify the read signal. The variable gain value is used to determine whether the head is functioning properly.

Abstract: Method of accurately measuring various kinds of non-linear transition shifts (NLTSs) in the magnetic recording/reproduction using an MR-type reproducing head is provided. According to the method, the data of a reference bit-string pattern are sent, as reference signals, to a magnetic disk 2 via a head IC 5 and a magnetic head 3 so as to be magnetically recorded. A first predetermined harmonic component Vnref is measured from the reproduced signals of the record data detected by the magnetic head 3, a bit-string pattern is selected from plural kinds of predetermined bit-string patterns, the data of the selected bit-string pattern are sent, as to-be-measured signals, to the magnetic disk 2, a second predetermined harmonic component Vnpat is measured from the reproduced signals, and the NLTS is calculated from Vnref and Vnpat.

Abstract: To fabricate a magnetic field sensor, a copper barrier film is formed. A magnetic metal film is formed on the barrier film. A plurality of trenches is formed with a desired thickness in the magnetic metal film. A copper film is formed in the plurality of trenches, so that multiple layers of magnetic metal film and copper film are formed. The RF semiconductor device equipped with the magnetic field sensor includes a magnetic field sensor made by the above method. The magnetic field sensor is attached on a semiconductor substrate. Metal wirings are formed at near the both sides of the magnetic field sensor. An insulating film is formed on top. An inductor is formed on the insulating film at predetermined locations.

Abstract: An object is to automatically detect the positions of spike noise, create a distribution diagram, and perform pass/fail decisions. The cross-correlation function of the signal waveform from a magnetic head 1 and a reference waveform simulating spike noise is used in extraction of spike noise. The number of peaks in the cross-correlation function exceeding a threshold value is counted, and quantitative evaluation of spike noise is performed.

Abstract: A magnetic field measurement system for canceling an external field is provided, in which plurality of sensing magnetometers (3) for measuring a magnetic field signal in a direction perpendicular to the center axis of a cylindrical magnetic shield (1) are arranged in two dimensions on a plane parallel to the center axis and a reference magnetometer (4) for measuring the external field parallel to the center axis as a reference signal is disposed on a plane perpendicular to the plane parallel to the center axis. The reference signal multiplied by a specified factor is subtracted from a difference between signals from the adjacent sensing magnetometers (3). The magnetic field measurement system allows measurement of an extremely weak magnetic field by efficiently canceling the external field.

Abstract: The present invention provides a method and apparatus for detecting the presence of contaminants on the slider of a disk drive. By detecting the rate of change of the resistance of a thin film coil of a disk drive write element during drive operation, it can be determined if a foreign material is present on the coil. Nominal resistance change values for write elements of a disk drive are determined at manufacturing time, and are stored within the disk drive. During later operational use, the resistance change for the coil of the write elements is measured and compared with the stored nominal resistance change values. If the difference between the stored nominal resistance values and the measured resistance change values exceeds a predetermined threshold, the drive is presumed to have contaminants on the slider.

Abstract: An apparatus for characterizing impedance presented to a write driver device in a write head assembly for use with an electromagnetic storage product includes: (a) a test impedance unit coupled with the write driver device; and (b) a measuring unit coupled with the test impedance unit. The measuring unit receives a measured parameter associated with the test impedance unit and compares the measured parameter with a reference parameter. The measuring unit indicates a result of the comparing.

Abstract: An apparatus for monitoring changes in a magnetic field using a magneto-resistive device situated in the field includes a first and second input locus coupled with the magneto-resistive device. An amplifier means for amplifying electrical signals has input terminals and output terminals. A first input terminal is coupled with the first input locus with a first capacitor coupled in series between the first input locus and the first input terminal. A second input terminal is coupled with the second input locus with a second capacitor coupled in series between the second input locus and the second input terminal. The apparatus receives a bias current at the first input locus that cooperates with the magneto-resistive element to affect electrical potential at the first input locus. The amplifier device presents at least one output signal at the output terminals indicating changes in the magnetic field.

Abstract: Methods and apparatus are disclosed determining the presence of base line popping noise for a read head inside an assembled disk drive, as well as, determining read bias conditions for operating the read head free of base line popping noise. These further include performance evaluation of the read head for read bias conditions free of base line popping noise. They also include repairing the read head using DC write current and read bias current within the assembled disk drive.

Abstract: A testing apparatus for testing a disk and/or head of a disk drive that includes a disk rotating device that rotates the disk and a rotary-positioning device that rotates and positions the head, with the rotary-positioning device supporting the head such that the attitude of the head relative to the center of rotation of the rotary-positioning device is tilted in comparison to the attitude of the head relative to the rotation center of the head in the disk drive.

Abstract: A method and apparatus produce a read signal using a read head. A variable gain value is set that is used by a variable gain amplifier to amplify the read signal. The variable gain value is used to determine whether the head is functioning properly.

Abstract: A lifecycle analyzer includes a heating element for heating a plurality of magnetoresistive (MR) elements, which maybe, e.g., in bar form. At one location the MR elements are in contact with a stress probe card for applying a bias voltage or current stress. The MR elements are moved to a separate location, where there is a test probe card and magnetic field generator for testing the MR elements after being stressed. In one embodiment, a subset of the plurality of MR elements is tested at a time. The lifecycle analyzer includes an in-situ abrasive element that is used to abrade the probe pins of the stress probe card to remove oxidation that results from extended contact with the heated MR elements.

Abstract: A transducer position sensing system in a disc drive to take frequent data measurements from micro-servo sectors on the disc and to interpret the information to predict recording failures. The disc drive is formatted with many small or micro-servo sectors containing, among other things, a servo address mark, encoded disc location information, and radial track position information. The sensing system frequently retrieves this information through the transducer, compares the measurements to expected values, and given unexpected measurements predicts errors. The time elapsed between the passing of servo address marks can be used to predict adjacent sector overwrites. The radial track position information can be used to predict off-track write errors. The radial track position signal amplitude can be used to predict the transducer moving too far from the disc, resulting in skip write errors.