Browse Prior Art Database

Multi Device Channel Operation

IP.com Disclosure Number: IPCOM000050161D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Brown, DT: AUTHOR [+2]

Abstract

This article describes an efficient means to copy data from one I/O device to another. Current channel programs in the IBM System/370 provide for data transfer between main storage (MS) and one I/O device as designated in the Start Input/Output (SIO) instruction. In order to copy data from one I/O device to another I/O device, two channel programs are required (the first to read the data from one I/O to MS and the second to write the data from MS to another I/O device), and some technique to synchronize the two channel programs. The consequence is that a large amount of processor time is consumed handling two SIO instructions for the two channel programs and their ending interrupt processing.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 61% of the total text.

Page 1 of 2

Multi Device Channel Operation

This article describes an efficient means to copy data from one I/O device to another. Current channel programs in the IBM System/370 provide for data transfer between main storage (MS) and one I/O device as designated in the Start Input/Output (SIO) instruction. In order to copy data from one I/O device to another I/O device, two channel programs are required (the first to read the data from one I/O to MS and the second to write the data from MS to another I/O device), and some technique to synchronize the two channel programs. The consequence is that a large amount of processor time is consumed handling two SIO instructions for the two channel programs and their ending interrupt processing. The method in this article reduces the CPU overhead by providing a single channel program which can both read from one device and then write to a second device under the control of a single SIO instruction, under which one channel program can copy an entire file from one device to another. This method can also control a data transfer between more than two I/O devices, e.g., reading from one device while writing on plural devices.

The first (Primary) I/O device is identified by the operand of a SIO instruction as in current System/370 architecture. Another (Secondary) I/O device is selected in the channel program by a new channel control word (CCW), herein called "designate secondary device (DSD)", which specifies a location in main storage that...