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Flexible Priority Mechanism for Resolution of Multiple Requests to System Storage

IP.com Disclosure Number: IPCOM000040610D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 3 page(s) / 46K

Publishing Venue

IBM

Related People

Cole, CW: AUTHOR [+2]

Abstract

In a controller system in which services are allocated to a plurality of input/output devices on a priority basis, the channel control element is designed to accept requests from many requesters, including an I/O Processor (IOP), a number of channels, and the channel subsystem timer. It must also accept storage requests of many different levels where the level is based on the identification (ID) of the requester and the type of request. It should also prevent any one requester from being forever "locked out" by higher priority requests from the other requesters. Finally, it should permit the priorities assigned to each requester to be set under software control which in turn permits the designers to "tune" the system as the system evolves through design, verification, test, and installation.

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Flexible Priority Mechanism for Resolution of Multiple Requests to System Storage

In a controller system in which services are allocated to a plurality of input/output devices on a priority basis, the channel control element is designed to accept requests from many requesters, including an I/O Processor (IOP), a number of channels, and the channel subsystem timer. It must also accept storage requests of many different levels where the level is based on the identification (ID) of the requester and the type of request. It should also prevent any one requester from being forever "locked out" by higher priority requests from the other requesters. Finally, it should permit the priorities assigned to each requester to be set under software control which in turn permits the designers to "tune" the system as the system evolves through design, verification, test, and installation. Referring to the drawing, a priority system adapted to meet these criteria operates in the following sequence. - Requester / determines that it wishes to store

data in system storage. Requester / places the

storage request commands on the Request / bus,

places his ID on the RID/ bus and raises the

request valid line (RV×)

- The Priority mechanism control logic, in response

to RV×, gates Request× and RID× to the Priority

Value Selection Logic.

- The Priority Value Selection Logic addresses one

location within the Priority Table which contains

an array of priority values loaded at system

start. The priority value stored in the addressed

Priority Table location is selected and is latche...