Abstract: Apparatus and method of even harmonic distortion compensation are provided for digital data detection in a disk file. The disk file includes a magneto-resistive (MR) head or other magnetic transducer head and an analog-to-digital converter (ADC) for providing a sampled readback signal. An even harmonic filter is coupled to the ADC for providing a filtered readback signal having only even harmonic components. An adder subtracts the filtered readback signal from the sampled readback signal for providing a compensated output signal. The compensated output signal is applied to a digital channel of the disk file.

Abstract: A method and apparatus are provided for determining an adjustable precompensation value in a partial-response maximum-likelihood (PRML) data channel. The PRML data channel includes an adjustable precompensation function for modulating the write data waveform. A predetermined test pattern is written using write circuitry in the disk file. The predetermined test pattern is insensitive to channel misequalization and provides a reference for gain and timing control. The written predetermined test pattern is read back using read circuitry in the disk file. An error in sample values in the read back predetermined test pattern is identified using logic provided in the PRML data channel while performing a standard read operation of a data sector written with the test pattern. The adjustable write precompensation value is adjusted responsive to identifying an error.

Abstract: The back edge of a disk drive slider is used to remove debris from disk media by slowly sweeping it from the inner diameter of the disk to the outer diameter of the disk while the disk is rotating backwards from normal. The sweeping operation is completed while the disks are still gaining rotational speed so that liftoff velocity is not achieved. Material accumulated on the back edge of the slider is either dumped at the outer diameter of the disk, or remains on the back edge of the slider as normal operation is commenced.

Abstract: Apparatus and method are provided for servo signal demodulation using a servo processor and a partial-response maximum-likelihood (PRML) data channel in a disk file. A servo burst timing window is identified. Then a plurality of digital samples are detected with the PRML data channel responsive to identifying the servo burst timing window. Sequential sets of the detected digital samples are accumulated by the PRML data channel and transmitted to the servo processor. The digital samples are processed by the servo processor for providing servo phase information that is used to provide servo position information.

Abstract: A thin film magnetic recording disk that has a layer of lubricant bonded thereto is enclosed within a vapor phase lubricant system that operates to continuously apply lubricant vapors to the disk's bonded lubricant layer by operation of Langmuir kinetics. Lubricant vapors are selectively adsorbed on the disk, including regions of the disk where the bonded lubricant is either too thin or is entirely absent, thus minimizing failures that might be caused by such imperfections in the bonded lubricant layer. A reactive perfluoropolyether (PFPE) lubricant containing chemically active functional groups is substantially bonded onto the recording surface of the disk, for example by the application of heat. The mobile residue of this bonded lubricant layer may be left on the disk, to thereafter function as a non-bonded, mobile, lubricant layer covering the surface of the bonded lubricant layer.

Abstract: An ECC decoder is provided for use with variable block lengths of Reed-Solomon (RS) code for on-the-fly detecting of multiple errors and correction of one error byte per interleave in data recorded on a storage medium in blocks. Each data block includes variable length data subblocks equal to N*L, where N equals a variable number of bytes per interleave and L equals the interleave degree. The ECC decoder includes a delay register for sequentially receiving consecutive N*L data bytes of the data subblocks at a delay register data input and for sequentially transferring the consecutive N*L data bytes of data subblocks to a delay register data output. Each subblock contains a predetermined number of error check bytes M. Multiple M partial syndrome generators sequentially receive the consecutive subblocks of data and generate partial syndromes. The generated partial syndromes are compared to identify agreement.

Abstract: Viterbi trellis coding methods and Viterbi detector apparatus are provided for detecting trellis coded data. A systolic array Viterbi detector recursively calculates path metrics and partial sums of metric update equations to determine codeword sequences having minimum mean squared error for Viterbi-type maximum-likelihood data detection. The systolic array Viterbi detector is arranged to eliminate redundant calculations and simplify hardware requirements. Modified butterfly trellis geometries and rotating state metrics arrangements are provided for simplifying the Viterbi detector.

Abstract: Disclosed is a bus expansion unit for extending the bus of a computer system which has an asynchronous bus cycle. The bus expansion unit includes an asynchronous state machine which uses a delay line to determine some of its states. The bus expansion unit recognizes the address and bus status and holds or latches a select signal. In addition, the bus expansion unit delays the -CMD signal until the peripheral has the opportunity to place valid data on a bus channel. In addition, the bus expansion unit includes an arbitration circuit for the peripheral attached thereto.

Abstract: To provide a magnetic disk apparatus in which an outline of a seal for hermetically sealing is identical with that of a cover and base having steps at the periphery thereof. In a sealed magnetic disk apparatus in which a cover and base having steps at the periphery thereof are joined together via a seal, two slopes 48 and 50 are provided, in a turned or stairs-like form, at each step portion at the periphery of a cover 60 and a base 40. The first slope 48 descends from the periphery toward the inside, and the second slope 50 connecting to the first slope descends from the inside toward the periphery. The slopes of the cover are provided to mate with those of the base, respectively. A seal 70 has an outline which is substantially identical with that of the cover 60 and the base 40 and includes projections 72 and 74 covering the slopes.

Abstract: A disk file includes an expansion ring attached to the wall of the hub and which is located between the lowermost disk of the disk stack and the hub flange. A circular ridge concentric with the hub is formed on the ring and engages the underside of the disk. The ring is adapted so that the thermal expansion of the ring is substantially equal to that of the aluminum disk at the position of contact between the two. A washer interposed between ring and flange allows the ring to move freely relative to the flange. During thermal cycling, the ring and disk move at the same rate at the point of contact, the ring ensuring that the disks remain concentric with the hub throughout the range of disk file operating temperatures.

Abstract: Disclosed is a disk drive for storing representations of data. The disk drive includes a housing or enclosure. At least one disk is rotatably attached to the housing. Also attached to the housing is an actuator. A transducing head is attached to one end of the actuator and is positioned to pass near the disk. Attached on the other end of the actuator is a coil which makes up a portion of a voice coil motor. Another portion of the voice coil motor is a magnet positioned near the coil. The housing includes at least one recess or opening which holds the magnet on the outside of the housing yet near the coil. A material which has low magnetic permeability or no magnetic permeability may be used to seal the opening or recess.

Abstract: In the slider 1 on which a transducer 5 is mounted and which moves above a recording surface 4, in order to generate different vibration modes according to various situations such as vertical lift-off and landing, and breaking away from stiction, etc. A plurality of piezo-electric elements 8A, 8B, 8C, and 8D are disposed on the slider 1 and means for supplying a different AC voltage to each of the piezo-electric elements 8A, 8B, 8C, and 8D is provided.

Abstract: A controller device interfacing method and a low level device interface are provided for use between at least one controller and a plurality of devices in a direct access storage device. Message and command and data information are received and transmitted between the controller and the device. Responsive to a received predetermined read data command, read data function hardware transmits the requested data to the controller. Responsive to a received predetermined write data command, write data function hardware writes the received data from the controller to a device. Received message information is blocked from received data information so that message information is transmitted at any time within and between data information transmissions. The low level device interface supports two wire serial data transfer and provides improved data rate performance.

Abstract: The lubricant film for a near contact magnetic recording device is maintained by a closed loop servo control for a recirculating lubricant supply system. A reservoir closely overlies the disk data surface and includes a heater for controlling the temperature difference between the reservoir and the disk surface. Decreasing the heater current reduces the film thickness and increasing the heater current increases the film thickness. A wick system gathers lubricant from within the disk enclosure, which may have been spun off the disk or condensed from the lubricant laden atmosphere and returns the lubricant by capillary action to the reservoir. Further, the reservoir includes two portions which are independently controllable. The first overlies the data band of the disk and the second overlies the start/stop zone and the head when the latter is not operational and parked at the nonoperating location.

Abstract: A method and apparatus are provided for digitally correcting sector pulse placement in a direct access storage device. A sector clock signal is generated equal to a sub-multiple clock rate of a predetermined servo identification clock. An individual servo identification field location is identified and compared with an expected location of said individual servo identification field to identify an error value. The sector clock signal is modified by adding or subtracting clock pulses responsive to the identified error value for generating a sector pulse.

Abstract: In a rigid magnetic recording disk, the magnetic properties, such as the coercivity, of a cobalt based, hard, magnetic alloy, such as a cobalt-platinum-chromium (CoPtCr) thin film magnetic recording layer, are controlled by providing a thin, sputtered, underlayer of a nonmagnetic, binary, chromium-tungsten (CrW) alloy whose major constituent is chromium, and preferably of a composition Cr.sub.88 W.sub.12 upon which the thin film magnetic recording layer is subsequently sputter deposited.

Abstract: Disclosed is a disk drive having at least one disk. An actuator arm carriers at least two sliders which are positioned over the first and second surface of the disk. The actuator arm moves the sliders to various selected positions over disks so that representations of data can be read from or written into the tracks of the disk. Each slider includes at least one magnetic transducer or magnetic head. The magnetic head is actually passed over the track in the disk during a read or write operation. The heads are shifted slightly with respect to a line perpendicular to the disk surface to minimize or reduce crosstalk and electromagnetic coupling between the heads located on the first and second surface of the disk. In other words, the heads are intentionally misaligned to increase the distance between the two heads and to reduce crosstalk and electromagnetic coupling between the two heads.

Abstract: A spindle motor control method and apparatus for spindle motor control are provided for use in a direct access storage device. A plurality of operational modes of the direct access storage device are detected. The operational modes of the direct access storage device include start-up and idle operational modes and predetermined critical operational modes that include reading of data and reading of servo information. A pulse width modulation (PWM) mode control for applying driving current to the spindle motor is provided responsive to detecting a start-up or an idle operational mode. A linear mode control for applying driving current to the spindle motor is provided responsive to detecting one of the predetermined critical operational modes. During operation of the disk file, a small percentage of the overall file power-on time is spent performing critical file operations so that substantial power savings are achieved by the PWM mode control.

Abstract: Disclosed is a slider with an air bearing surface for flying a magnetic transducer on an air lubrication film over a moving recording medium. The air bearing surface allows the slider to fly at a close and substantially uniform height over the disk surface regardless of the skew angle of the air flow. The slider has a pair of nonidentical, nonsymmetrical rails disposed about the longitudinal axis of the slider, which through the viscous effects of the air flow, provide the air lubrication film when the recording medium is in motion.

Abstract: A rotating magnetic storage device is shown wherein the transducer and media are separated during operation by a thin film of low viscosity liquid lubricant that is recirculated from a reservoir within the head-media enclosure. Lubricant recirculation can be effected by capillary action using a wick, mechanical pumping and metering or distillation techniques. As compared to devices using air bearing separation, the transducer carrying slider has very small bearing surfaces which may be in the form of narrow rails or small depending foot elements. This enables fly heights of 2 microinches using a film of one micron thickness.