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Auxiliary Input Output Processor Using Shared Storage and a Uniform Instruction Set

IP.com Disclosure Number: IPCOM000045186D
Original Publication Date: 1983-Feb-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 3 page(s) / 59K

Publishing Venue

IBM

Related People

Giangarra, PP: AUTHOR [+2]

Abstract

Storage and Central Processing Unit (CPU) load on a minicomputer is reduced and the software device support is transferred to an outboard processor. Shared storage is used to prevent an additional data transfer between the devices and main storage and a uniform instruction set (the one used by the CPU) is used to ease code migration and the programming of the I/O processor.

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Auxiliary Input Output Processor Using Shared Storage and a Uniform Instruction Set

Storage and Central Processing Unit (CPU) load on a minicomputer is reduced and the software device support is transferred to an outboard processor. Shared storage is used to prevent an additional data transfer between the devices and main storage and a uniform instruction set (the one used by the CPU) is used to ease code migration and the programming of the I/O processor.

An addressing range for input/output operations of eight 64KB address spaces is encountered in a minicomputer, such as the IBM Series/1 system because there are 3 bits allowed for the address key in the control word of the Device Control Block (DCB) and 16 bits for the buffer address. The device management control blocks require a considerable amount of storage in address space 0. Also, the processing required to support devices consumes CPU time.

Here, a processor is added to handle all I/O operations and replaces the current Series/1 channel. By using the Series/1 architecture for the I/O processor, much of the function of the device management routines can be moved to the I/O processor, resulting in a storage saving on the CPU and more overlap between I/O and processing. In addition, all existing Series/1 devices can be attached via the Series/1 channel to the processor. By using shared storage, data is moved directly from the main storage of the CPU to the device or from the device to main storage. Also, the I/O processor permits the development of most device support code in a simple environment, and this code does not have to be duplicated for each Series/1 operating system.

The system in Fig. 1 shows an IBM Series/1 CPU 1 having an attached processor 2 that is referred to as the I/O processor. Processor 2 is a standard Series/1 processor with the following features: - 64KB of local storage 3

- an address translator with eight banks of segmentation

registers

- a Series/1 channel that allows the attachment of I/O

device 4.

The I/O processor is also attached to the storage bus of the CPU 1 in such a manner that all of the storage 5 of...