Browse Prior Art Database

Command Streaming

IP.com Disclosure Number: IPCOM000052593D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Court, JF: AUTHOR [+2]

Abstract

In contemporary data processing systems, certain communications between I/O channels and device control units must be conducted within a "critical time" period. When this period is exceeded, the operation terminates abnormally in an overrun, requiring the central processing system to undertake lengthy analysis and recovery procedures which interfere with central processing productivity. This is particularly true, for instance, in respect to the transmittal of certain chained channel command words (CCWs) from channels to device control units where a time dependency exists between the performance by a control unit of operations specified by successive CCWs of a chain. A technique described presently ensures timely transmittal of such time-interdependent chained CCWs over standard channel to control unit interfaces.

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Command Streaming

In contemporary data processing systems, certain communications between I/O channels and device control units must be conducted within a "critical time" period. When this period is exceeded, the operation terminates abnormally in an overrun, requiring the central processing system to undertake lengthy analysis and recovery procedures which interfere with central processing productivity. This is particularly true, for instance, in respect to the transmittal of certain chained channel command words (CCWs) from channels to device control units where a time dependency exists between the performance by a control unit of operations specified by successive CCWs of a chain. A technique described presently ensures timely transmittal of such time-interdependent chained CCWs over standard channel to control unit interfaces.

In contemporary systems, an I/O channel in communication with a control unit normally transmits one CCW at a time, each accompanied by a "command out" tag signal (refer to "IBM System/360 and System/370 I/O Interface Channel to Control Unit OEMI,"GA 22-6974 ), and follows up each CCW transmittal by waiting for a responsive signal from the control unit indicating the status of its reception of that CCW. Thereafter, the channel and control unit usually exchange other signals associated with the operation specified by the CCW.

In furtherance of the present objective of providing timely CCW transmittals, it is proposed that contemporary cha...