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Browse Prior Art Database

System-Assignable Data-Compression Mechanism

IP.com Disclosure Number: IPCOM000041887D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 3 page(s) / 44K

Publishing Venue

IBM

Related People

Dixon, JD: AUTHOR [+3]

Abstract

This mechanism enables the user of a data processing system to cause compression of the data being stored in or retrieved from a magnetic disk data storage file for those applications where compression is desired for either the storing operation or the retrieving operation. Such data compression capability is particularly advantageous for disk save/store operations and also for purposes of increasing the amount of data that may be stored in a disk file. In the illustrated embodiment, the data processing system includes a host processor 10 having associated therewith a main storage unit 11 and an I/O channel bus 12 for connecting various peripheral devices to the host processor 10.

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System-Assignable Data-Compression Mechanism

This mechanism enables the user of a data processing system to cause compression of the data being stored in or retrieved from a magnetic disk data storage file for those applications where compression is desired for either the storing operation or the retrieving operation. Such data compression capability is particularly advantageous for disk save/store operations and also for purposes of increasing the amount of data that may be stored in a disk file. In the illustrated embodiment, the data processing system includes a host processor 10 having associated therewith a main storage unit 11 and an I/O channel bus 12 for connecting various peripheral devices to the host processor 10. One such peripheral device is represented by a magnetic disk file 13 which is connected to the channel bus 12 by a disk control unit 14, and another such peripheral unit is represented by a magnetic tape unit 15 which is connected to the bus 12 by way of a tape control unit 16. Data is transferred between the bus 12 and the disk file 13 by way of a data register 17, a path selector 18 and one or the other of a data bus 19 and a data compression unit 20. The internal operation of the disk control unit 14 is controlled by a microprocessor 21 which receives user commands from the host processor 10 by way of a command register 22. Among other things, the microprocessor 21 controls both the path selector 18 and a direction control unit 23 which controls the direction of data flow through the data compression unit 20. In response to the appropriate user command, the microprocessor 21 will set the path selector 18 to cause data to flow by way of one or the other but not both of the data bus 19 and the data compression unit 20. For the case where the data compression 20 is selected, the user command also contains direction control information for enabling the microprocessor 21 to set the direction control unit 23 to provide the desired direction of data flow through the data compression unit 20. In particular, the direction control unit 23 switches the input and output terminals of the data compression circuit in the unit 20 so that, in one case, data coming from the disk file 13 is compressed and supplied to the path selector 18 and, in the other case, data coming from the path select...