Browse Prior Art Database

Nonprioritized Queue Selection Mechanism

IP.com Disclosure Number: IPCOM000083533D
Original Publication Date: 1975-Jun-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Callahan, RW: AUTHOR [+2]

Abstract

A number of users (queues) sharing a common service equipment under microprogram control may be given effectively equal service access by rotating priority. A simple but effective priority rotation scheme is given below.

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Nonprioritized Queue Selection Mechanism

A number of users (queues) sharing a common service equipment under microprogram control may be given effectively equal service access by rotating priority. A simple but effective priority rotation scheme is given below.

Eight place shift register SB is initialized in state 00000001 (hex 01) shown in Fig. 1. Individual triggers EE indicate immediate service request states of individual users of a group of six users. Work latch WL indicates a need for service by one or more members of the group.

Set state of WL branches the control microprogram (Fig. 2) at the appropriate entry point (2-1) to the Group Service Assignment (GSA) subsequence. Bits of SB are examined in predetermined order (2-2, 2-3, 2-4) until the "1" bit (initially in the first "bit 8" position) is located. Then SB is shifted left one position and the sequence is branched on the state of the respective trigger EE (e.g., EE1 associated with user 1 for the initial state of SB).

If the associated user (e.g., user 1) does not require service, the GSA sequence is reentered (2-5). If service is required, a group status bit STB (which may be in fast access local storage) is reset and a service subroutine is evoked (2-6).

The main control sequence is thereafter reentered (2-7) and with each reentry to the GSA subsequence the above is iterated, for successive shift states of SB, with user priority thereby effectively rotated.

After six iterations the priority rotation...