Input/Output Configuration Program: Difference between revisions

Revision as of 04:07, 17 May 2018

Revision as of 15:14, 7 December 2021

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{{about|Input/Output Configuration Program|the IOCP API|Input/output completion port}}

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{{Infobox software

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InThe '''Input/Output Configuration Program''' in [[computing]] was part of the original [[IBM System/360|S/360]] and [[IBM System/370|S/370]] architectures,. eachEach processor had its own set of I/O channels and addressed I/O devices with a 12-bit ''cuu'' address, containing a 4-bit channel number and an 8-bit unit (device) number to be sent on the channel bus in order to select the device; the operating system had to be configured to reflect the processor and ''cuu'' address for each device. The operating system had logic to queue pending I/O on each channel and to handle selection of alternate channels. Initiating an I/O to a channel on a different processor required causing a [[Shoulder tap (software)|shoulder tap]] interrupt on the other processor so that it could initiate the I/O.

In the original [[IBM System/360|S/360]] and [[IBM System/370|S/370]] architectures, each processor had its own set of I/O channels and addressed I/O devices with a 12-bit ''cuu'' address, containing a 4-bit channel number and an 8-bit unit (device) number to be sent on the channel bus in order to select the device; the operating system had to be configured to reflect the processor and ''cuu'' address for each device. The operating system had logic to queue pending I/O on each channel and to handle selection of alternate channels. Initiating an I/O to a channel on a different processor required causing a [[Shoulder tap (software)|shoulder tap]] interrupt on the other processor so that it could initiate the I/O.

Starting with the [[IBM 3081]] and [[IBM 4381]] in [[IBM System/370#Expanding the address space|S/370-Extended Architecture]]<ref name=SA22-708>{{cite manual