Abstract: A method of detecting certain runs of data, such as identical consecutive runs of data, is disclosed. The logical operation exclusive OR (XOR) is performed on each pair of adjacent bytes in a source string of data bytes in a single machine instruction, resulting in a comparison data string of bytes. The comparison data string is then sequentially searched for a byte which matches a predetermined byte. In the case of a search, the predetermined byte may be any value, which value is determined by the XOR of two adjacent bytes that are to be found. In the case of compression, as used in this invention, the predetermined byte has a value of zero, indicating that two adjacent bytes in the source string are identical. The sequential search occurs in a single Translate and Test (TRT) machine instruction. Once an all-zero byte is located, the subsequent byte in the comparision data string is examined.

Abstract: An interleaved head for reading and writing data transitions onto a magnetic tape. A magnetic recording system for the bi-directional transportation of the tape media across the interleaved head. A controller controls the tape drive in a reel-to-reel format to accomplish the bi-directional motion of the tape media. The interleaved head includes two modules with each module having a plurality of alternating read and write transducers alternately spaced apart along a single line placed transverse to the movement of the magnetic tape. The two modules are placed together such that the write gaps of one module are aligned with the read gaps of the other module. Each read module includes the magneto-resistive element. Each write transducer includes a thin film conductor driving a nickel zinc ferrite substrate as one pole piece and a nickel zinc closure piece as the second pole piece.

Abstract: The invention is a cleaning cartridge which includes a housing and a tube for injecting a compressed gas therethrough and into specific areas of an optical disk drive. The tube is removably connectable at one end to a compressed gas supply, and is aimed at the other end to direct gas exiting therefrom at both the objective lens, beam-directing prism or mirror, or other internal optical disk drive components when the cartridge is seated in the drive. Upon insertion of the cleaning cartridge into the optical disk drive in the usual manner for any optical disk cartridge, gas is released from the compressed gas source, through the tube, and into the optical disk drive. The use of such a cleaning cartridge provides for easy, effective cleaning of any internal optical disk drive component without the abrasion and potential inconveniences associated with mechanical brushing, wiping, or other techniques.

Abstract: An interleaved bi-directional magentic tape head for contact recording can have a poletip enhanced by providing a thin film of a soft magnetic material deposited onto a magnetic ferrite substrate. The second pole piece is a thin film of the soft magnetic material. A closure block of a non-magnetic ceramic encloses the layers together with leveling insulation layers and a deposited activating conductor turns. The stripe poletip deposited onto the magnetic ferrite extends for a distance just short of the first conductor turn and provides a balancing of the saturation moment of the pole pieces and provides for better recording capability, especially when operating in a trailing magnetic ferrite mode.

Abstract: A method for dispatching work requests in a data storage hierarchy in which directory data is promoted in variable length spans, the use of which are maximized even for work requests entering the work request queue after the span is chosen, is disclosed. A queue of work requests is initially scanned to determine if any requests therein require access to directory data stored in secondary storage within a prescribed proximity of that required by the next request to be dispatched. If such other work requests exist, then directory data in addition to that required by the next request to be dispatched is also promoted. To minimize seek time and rotational latency, the additional data is promoted from secondary storage in a single device I/O cycle. The additional data is chosen by adjusting the outer limits of the span as each work request in queue is scanned. After the actual promotion of the span of data, the existing work request is completed.

Abstract: An improved method of tracing the paths used in execution of a computer program is disclosed. The method includes using the state of a single bit to denote the referencing of a trace point in the program. The trace points are logically located near the program branch points. One or more bit maps are arranged in a known state at the beginning of program execution and the state of a particular bit in one of the bit maps is set when the associated trace point is referenced. Each bit is associated with a particular trace point according to its position in the bit maps. After program execution, the bit maps are compared to the source listing to determine which trace points were referenced. The use of single bits to denote the referencing of trace points minimizes the degradation of performance efficiency of the target program.

Abstract: A method for servicing a mount request in an automated storage library in which all of the peripheral storage devices therein are occupied and which permits an active data storage medium to be temporarily demounted and subsequently remounted in any subsequently available peripheral storage device is disclosed. To service a mount request requiring that a data storage medium be demounted, the access information for the data storage medium to be demounted is first retained. After demounting and servicing of the mount request, the retained access information is used to permit remounting of the previously mounted data storage medium in any subsequently available peripheral storage device, thereby minimizing the risk of delay in remounting. The method also allows for optional parameters to prevent temporary demounting in an automated storage library, or to prevent temporary demounting of particular data storage media. An automated storage library and program product employing the method are also disclosed.

Abstract: A tape support which provides several different functions in a reel-to-reel tape drive is disclosed. The tape support provides means for sensing tension in the tape, buffers or decouples the tape at the magnetic head from any perturbations arising at the take-up reel, and reliably guides the tape along the tape path. The tape travels along an arcuate surface of the tape support on an air bearing. A port in the arcuate surface senses pressure between the tape and the arcuate surface. This pressure is communicated to a transducer which provides an output representing the tension on the tape. Flanges on the ends of the tape support provide guiding of the tape over the air bearing and also provide venting of the air bearing to prevent tape vibration. A purge line expels a gaseous medium out of the sense port thereby keeping the sense port clear of contaminants.

Abstract: An improved thin magnetic layer which is suitable for use in magnetic head pole piece applications and a method of manufacture therefor are disclosed. The magnetic layer is a single phase composition of NiFe and Al.sub.2 O.sub.3. The magnetic layer is manufactured by cosputtering from a single, two phase sputtering target, or from separate NiFe and Al.sub.2 O.sub.3 sputtering targets. The single phase composition results in increased abrasion resistance without degradation of the magnetic properties of the layer.

Abstract: A reconfigurable parallel group of identical functional units and a method for reconfiguring this parallel grouping of identical functional units upon the occurrence of a failure by shifting the contents of the failed unit and the contents of all units between the failed unit and a spare unit one unit toward the spare unit is disclosed. A paired system of input and output busses allows control lines to activate and deactivate the appropriate busses so that a constant input output interface is maintained despite the failure provoked shift. This reconfigurable parallel group can also be stacked together to form larger configurations.