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Mechanism in a Distributed Data Processor System to Reduce Context Changes Due to Interrupts

IP.com Disclosure Number: IPCOM000035054D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 6 page(s) / 63K

Publishing Venue

IBM

Related People

Hall, WD: AUTHOR [+2]

Abstract

This article describes a technique wherein multiple I/O interrupts and I/O commands service an asynchronous, unsolicited input. System architectures which support a full duplex view between any facility and its software, allow input data to be accepted without incurring the overhead of an interrupt, issuance of an I/O command and another interrupt. This is accomplished by providing each facility with two forms of control blocks which can be used concurrently. They are solicited and unsolicited. To support this system level architecture, a set of orders are defined in the architecture for an insertion ring to identify unsolicited input data frames separately from frames which are solicited read or writes requested by the attached processor.

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Page 1 of 6

Mechanism in a Distributed Data Processor System to Reduce Context Changes Due to Interrupts

This article describes a technique wherein multiple I/O interrupts and I/O commands service an asynchronous, unsolicited input. System architectures which support a full duplex view between any facility and its software, allow input data to be accepted without incurring the overhead of an interrupt, issuance of an I/O command and another interrupt. This is accomplished by providing each facility with two forms of control blocks which can be used concurrently. They are solicited and unsolicited. To support this system level architecture, a set of orders are defined in the architecture for an insertion ring to identify unsolicited input data frames separately from frames which are solicited read or writes requested by the attached processor. In a distributed data processor (DDP) system, such as the one disclosed in [*], the Start Unsolicited orders are issued by the port to allow a drop to initiate an unsolicited operation to the port. All the information required by the drop to initiate the unsolicited operation is contained in the Start Unsolicited order frame. These orders do not cause the drop to appear busy to the port. The following information is sent as part of the Start Unsolicited orders: Drop Control Data - The twelve drop control data bytes contain the control

information and

counts associated with the

control and

disciplining of the drop by

the port. The order code is defined next to the order name in each section. The format of the start unsolicited orders is defined as follows: The Unsolicited Data orders are used to transfer unsolicited data from a drop to a port which has allowed the data. These orders indicate to the port that all the data allowed could not be transferred in this frame and additional Unsolicited Data orders and/or an Unsolicited Data and Interrupt order is required to complete the data transfer. Therefore, these orders represent an initial order or a continuing order in an information unit. These orders may be issued to a port, only if the drop has received a Start Unsolicited order from the port. Additionally, the drop should not issue this order, if the drop has previously issued an unsolicited information unit and has since not received another Start Unsolicited order from the port. The following information is sent as part of the Unsolicited Data order: Address Disp - The address displacement is a sixteen-bit logical displacement from the associated

main storage address. Transfer Count -

The transfer count is a sixteen-bit count which defines the number of data bytes con

tained in the order frame. The order code is defined next to the order name in each section. The format of the Unsolicited Data orders is defined as follows: The Unsolicited

1

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Interrupt orders are used to transfer ending interrupt information associated with an unsolicited operation or an unsolicited data transfer from a dro...