Browse Prior Art Database

Program Controlled Interrupt Priority Mechanism

IP.com Disclosure Number: IPCOM000085801D
Original Publication Date: 1976-Jun-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Meredith, VE: AUTHOR [+2]

Abstract

A priority mechanism is described for handling program controlled interrupts (PCI's) in a more efficient and timely manner.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 71% of the total text.

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Program Controlled Interrupt Priority Mechanism

A priority mechanism is described for handling program controlled interrupts (PCI's) in a more efficient and timely manner.

Existing microprogrammed data processors frequently do not provide sufficient priority for PCI interrupts to effectively support time dependent peripheral devices. PCI interrupts can exist in a dormant state in an input/output (I/O) channel and are not presented when the central processor unit (CPU) is enabled.

The solution is to provide a priority mechanism to insure that a pending PCI interrupt can be loaded in the channel interrupt buffer, during the period of time required by the interrupt handler in the CPU to process the previous interrupt. This is accomplished by the following: 1. Raise the priority of the byte multiplexor channel PCI. a. Raise byte multiplexor channel priority above selector channels.
b. Raise PCI priority to same level as Channel End interrupts. 2. Have the byte multiplexor channel remember dormant PCI's and retrieve them from the Unit Control Word (UCW) when the interrupt buffer is empty. a. Extend the Interrupt buffer (probably in control storage) to include: 1) The PCI bit. 2) A dormant PCI flag byte. 3) An address list for dormant PCI's. The size of items 2 and 3 would depend on the maximum number of dormant PCI's to be supported. b. Set PCI flag in the extended interrupt buffer when the interrupt buffer is filled for a PCI. c. If the interrupt buffer is full when...