Abstract: A method and computer system having a processor are provided for selectively compressing a data communication frame for data transfer between the computer system and at least one other system. A processor work load is periodically identified for the processor. A predetermined stored threshold value is identified and compared with the identified processor work load. Responsive to an identified processor work load greater than the identified predetermined threshold value, the data communication frame is transmitted without compressing the data communication frame. Otherwise the data communication frame is compressed and then transmitted responsive to an identified processor work load less than or equal to the identified predetermined threshold value. A state of a communication line is identified for the data transfer. Responsive to an identified idle state of the communication line, the data communication frame is transmitted without compressing the data communication frame.

Abstract: A disk drive includes a cast base upon which is mounted the disk stack-spindle assembly and the actuator assembly and a cover that is loosely received by the cast base to form the head-disk enclosure. The cover is secured and sealed to the cast base by a malleable metal foil tape that surrounds the enclosure and continuously overlies the interface between cover and base. The tape complies with the surface irregularities and does not creep, to provide permanent shielding and sealing between base and cover. Further, cables exiting the enclosure may be sealed using a piece of double sided adhesive which is interposed between cable and casting followed by application of the malleable foil tape thereover. Thus in a compact device, no significant thickness is added to the enclosure wherein a maximum available height is used to house the stack of disks while providing noise and EMC shielding in addition to securing and sealing the cover.

Abstract: In a process for manufacturing a rigid magnetic recording disk, the disk's rigid substrate member is subjected to a force that produces plastic deformation in a manner so as not to remove material therefrom. In this way, the disk is provided with a surface topography that contains a controlled texture, for example in the area of the disk's start/stop track. In an embodiment of the invention, an ultrasonic probe and a disk shaped substrate member are placed in close proximity within a container that holds a fluid abrasive slurry, i.e. a suspension of hard particles in a liquid. Operation of the ultrasonic probe, as the substrate member rotates, causes the slurry to texture an adjacent portion of the substrate member by means of plastic deformation and in the absence of material removal from the substrate member. Operation of the probe thus provides texturing of the disk at an inner diameter track area thereof, for example in the disk's start/stop area.

Abstract: Apparatus and method for providing equalization adjustment for a finite impulse response (FIR) digital filter are provided in a PRML data channel. A plurality of transformations are defined to transform effective tap weights in a digital filter into modified effective tap weight values by adding each said initial effective tap weight value with a selected cosine equalization adjustment function. A cosine expander circuit is provided for expanding 8-byte compressed equalizations into a 32-byte format and for altering the filter response by a selected cosine equalization adjustment function.

Abstract: A data storage device for use with a rotatable data storage medium having a data head and a controller for controlling movement of said data head characterized in that said controller varies the time taken for moving said data head between given positions in response to the state of said device. Particular embodiments of the invention coordinate the movement of the data head with the rotational position of the data storage medium so that the data head arrives at the desired position at the same time as the portion of the data storage medium to be accessed arrives beneath the data head. In other embodiments the time taken to move the data head between given positions is increased if the temperature of the mechanism for moving the data head exceeds a predetermined value.

Abstract: A rotary actuator head driver for a direct access storage device includes a transducer head moving in a radial direction across a disk surface for reading and/or writing data on a plurality of tracks for storing data. A support arm supports the transducer head relative to the disk surface. The support arm is connected to a pivot defining an axis of rotation spaced from the transducer head. A head driver positions the transducer head over one track in a track following mode or moves the transducer head from one track to another track in a seek mode. The head driver generates oppositely directed forces to produce a net torque applied to the support arm through the pivot. The oppositely directed forces have a line of action orthogonal a dominant motion of the transducer head. As a result, any parasitic force is orthogonal to the dominant motion and does not contribute to track misregistration errors.

Abstract: High density magnetic disk storage and semiconductor module technologies are combined to provide a disk drive using a standard multilayer ceramic substrate as the disk drive base support member to support spindle and actuator assemblies including 1 inch diameter disks. The ceramic substrate has components and very large scale integration (VLSI) chips mounted directly thereon to avoid use of one level of packaging and presents standard pins to mount the drive using standard sockets to afford economy and reliability.

Abstract: A 10-tap finite impulse response (FIR) digital filter is provided in a partial response signaling and maximum-likelihood (PRML) data channel. A plurality of partial sums of predetermined tap weights are stored in a palette random access memory (RAM). A fixed qualifier value is received and used together with selected ones of the stored partial sums for calculating a predetermined tap weight. Predetermined filter coefficients are calculated and stored in a filter RAM using the calculated predetermined tap weight and predefined ones of the stored partial sums.

Abstract: The flow of work requests in a server driven process to process communication environment is described. Logical connections between processes and bus managers interfacing bus units to an I/O bus are assigned to connection groups for management by the bus managers. Each bus unit has its own connection groups for the logical connections. Bus unit resources are assigned to each connection group based on performance factors, and a series of bus unit messages are used to control the flow of work so that a group which has no more resources will not accept further work requests. The originator of the work requests will resequence rejected work requests and resend them when the connection group has freed up resources. A further mechanism is provided to facilitate work consistent with the server driven architecture when bus units do not have adequate DMA capabilities. Two ways of reversing control of transfer of work requests and data so that the server need not have master DMA capability are presented.

Abstract: Apparatus and method for asynchronous servo identification (SID)/address mark detection are provided for data detection in a partial-response maximum-likelihood (PRML) data channel. The SID/AM pattern includes a first preamble section defined by a plurality of short magnets; a body section defined by a predetermined number of long magnets; and a delimiter section defined by a plurality of short magnets. Samples from the digital filter are applied to first and second correlation filtering paths. The first correlation filtering path includes a polarity threshold function to indicate one of a preamble section or a delimiter section of a SID/AM pattern. The second correlation filtering paths includes a second threshold function and a comparator for sequentially comparing sequential ones of the received samples responsive to identifying the second threshold value to identify a predefined sequence.

Abstract: A method and apparatus for modulating a data reference clock for rotational speed variations of the data storage disk in a direct access data storage file. A data reference clock is generated from an encoded disk rate clock of the data file. A readback signal from at least one predetermined region of the disk surface is sensed and a sync byte is detected responsive to the readback signal. An early window control signal and a late window control signal are generated corresponding to end boundaries for capturing readback encoded data signals. A load complete signal is identified responsive to the readback signal. The identified load complete signal with the early window control signal and the late window control signal and the generated data reference clock is adjusted responsive to overlapping compared signals.

Abstract: Disclosed is a disk drive having an enclosure for housing one or more disks, an actuator arm and sliders attached to the actuator arm. The sliders include magnetic transducers for reading information related to data off the disk and for writing representations of data to the disk. In a disk drive with an in-hub, fixed spindle shaft motor, the disk or disks are attached to the hub which is rotatably mounted to the spindle shaft. The hub includes one or more fingers attached to the hub which touch the spindle shaft when the hub is stationary and when the hub is rotating. The spindle shaft may also be provided with a wear resistant layer and/or ring of conductive material to enhance the electrical pathway between the hub and the spindle shaft and provide for lower wear and a longer life.

Abstract: A magnetic head/support assembly for incorporation in the data access mechanism of a disk file includes a magnetic head and assembly and a separate member for locating the head leads remotely from the head element. The head lead locating member preferably comprises a pair of adhesively bonded thin laminate strips, between which the leads are situated. The strips maintain the leads in a fixed spaced apart relationship for a sufficient portion of their lengths to permit direct electrical connection to a correspondingly spaced pattern of conductors on external data channel circuitry carried by the data access mechanism.

Abstract: In recording systems using partial-response maximum-likelihood detection (PRML) techniques, data sequences are preceded by a preamble consisting of all ones. Coding schemes are disclosed which allow to keep the number of consecutive ones occurring in the coded data sequences at a minimum, while simultaneously restricting the number of consecutive zeros in full and partial data sequences to a low value which is important for improving receiver operation. The disclosed coding schemes and apparatus enable a faster and more reliable discrimination between timing preambles and data sequences, thus allowing to use shorter timing preambles which results in faster receiver start-up and in a reduction of storage overhead for the preambles.

Abstract: A data processing system is disclosed having a direct access storage device (DASD) subsystem comprising a number of separate physical housings, each housing having a number of disk supporting spindles mounted therein. The velocity of rotation of the spindles within a housing is synchronized, and the rotational position of the spindles may be locked into a fixed relationship. When number N of disk supporting spindles are provided, spindle rotation is synchronized, and mirrored data files are written out of phase by 360/N degrees, thereby providing reduced latency time during a subsequent read operation, while at the same time providing data integrity through the use of redundant data files.

Abstract: The magnetic properties of a cobalt based, thin film, magnetic recording layer are controlled, independent of controlling the process for depositing the magnetic layer itself, by the introduction of process compatible dopant gases into an argon atmosphere during the vacuum deposition (i.e. a sputtering process or an evaporation process) of a chromium based underlayer upon which the magnetic layer is subsequently deposited. The same or a different dopant may also be introduced into the magnetic layer. The process compatible dopant gases described contain oxygen, nitrogen and/or carbon, and mixtures thereof, and include the group purified air, oxygen, nitrogen, a mixture of oxygen and nitrogen, carbon monoxide, carbon dioxide, methane and water vapor.

Abstract: Apparatus and method of thermal asperity compensation are provided for data detection in a partial-response maximum-likelihood (PRML) data channel. The PRML data channel includes an analog to digital converter (ADC) having a normal operating range and a filter, gain and timing control coupled to the ADC. When a thermal asperity is detected, a thermal asperity recovery mode is established responsive to the detected thermal asperity. The gain and timing control are held and the normal operating range of the ADC is adjusted responsive to the thermal asperity recovery mode. Also an AC coupling pole frequency is elevated responsive to the thermal asperity recovery mode.

Abstract: The vapor drain is a device that permits steady state control of the composition of the atmosphere within a substantially sealed enclosure. For any fabricated enclosure the will be sources of vapor phase molecules: molecules evaporating from a deliberately installed lubricant reservoir, molecules outgassed from components, and molecules diffusing in from the outside world. The purpose of the vapor drain is to minimize the second two classes of molecules in the composition of the enclosure atmosphere as they are considered to be contaminants. An example application is a rigid disk magnetic data storage device which requires a monomelecular layer of lubricant on the disk and slider surfaces. The vapor drains suppresses the contaminant population by capturing a portion of all three sources of molecules in the vapor phase.

Abstract: A method and apparatus are provided for controlling a digital filter function included in a data path within gain and timing control loops of a PRML magnetic recording channel. The digital filter function is removed from the data path during an acquisition mode and the digital filter function is restored to the data path during a tracking mode. A predetermined gain and a quantized delay at a synchronization frequency are provided when switching from acquisition mode to tracking mode. A unity gain and a delay of an integer number of sample periods are provided at a synchronization frequency when switching from acquisition mode to tracking mode.

Abstract: The flow of work requests in a server driven process to process communication environment is described. Logical connections between processes and bus managers interfacing bus units to an I/O bus are assigned to connection groups for management by the bus managers. Each bus unit has its own connection groups for the logical connections. Bus unit resources are assigned to each connection group based on performance factors, and a series of bus unit messages are used to control the flow of work so that a group which has no more resources will not accept further work requests. The originator of the work requests will resequence rejected work requests and resend them when the connection group has freed up resources. A further mechanism is provided to facilitate work consistent with the server driven architecture when bus units do not have adequate DMA capabilities. Two ways of reversing control of transfer of work requests and data so that the server need not have master DMA capability are presented.