Browse Prior Art Database

Open I/O Architecture for a High-Level Computer System

IP.com Disclosure Number: IPCOM000040375D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 3 page(s) / 30K

Publishing Venue

IBM

Related People

Collins, RW: AUTHOR [+4]

Abstract

The IBM System/38 high-level machine architecture provides a machine interface which is largely independent of hardware details. Hardware dependencies are absorbed by internal microcode functions that handle many machine dependencies including channel and I/O interface details. The advantages of high-level machine architecture include integrity, security and ease-of-use. The cost of providing such an architecture is, with respect to I/O, that the manufacturer must provide special microcode to include each I/O device in the machine interface. The effect is to close the machine interface to all but the I/O devices selected by the manufacturer; usually those popular devices most likely to be selected by many customers.

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Open I/O Architecture for a High-Level Computer System

The IBM System/38 high-level machine architecture provides a machine interface which is largely independent of hardware details. Hardware dependencies are absorbed by internal microcode functions that handle many machine dependencies including channel and I/O interface details. The advantages of high-level machine architecture include integrity, security and ease-of-use. The cost of providing such an architecture is, with respect to I/O, that the manufacturer must provide special microcode to include each I/O device in the machine interface. The effect is to close the machine interface to all but the I/O devices selected by the manufacturer; usually those popular devices most likely to be selected by many customers. Special I/O devices, likely to be of interest to a limited number of customers, are passed over and cannot be attached. The technique disclosed herein allows attachment and control of a large class of I/O devices to a high-level architecture computer system without requiring unique internal microcode special to each device while maintaining the integrity, security and ease-of-use of the high-level machine interface. Many standard I/O interfaces exist such as the IBM System/370 Channel. Each of these standard interfaces has a standard command structure with, at minimum, commands for READ, WRITE, CONTROL, and SENSE. Some interfaces define additional commands. The S/370 channel defines a READ BACKWARD command, SENSE ID, a special sense operation, and TRANSFER IN CHANNEL, a special control command, for controlling branching in channel programs. In most standard interfaces there are multiple commands of each type to accommodate variations in the different devices that will be attached. A key element of the technique disclosed herein is the observation that all the commands on a standard interface can be reduced to three classes: READ, WRITE, and READ BACKWARD. When viewed at the level of data transmission, the CONTROL commands can be treated as writes, SENSE as reads, and so on. A second key element is the observation that internal microcode can be written for the System/38 specifical...