Richard Roland Guyette

System/370 extended architecture: the channel subsystem

The 370-XA channel subsystem architecture represents a significant extension of the corresponding System/370 architecture. This paper examines the need for these extensions, discusses the important features and facilities of the new architecture, and provides comparisons with its predecessor, the System/370 channel architecture. It also describes, from an operational viewpoint, how these new concepts affect I/O processing and how they relate to the current trend toward using multiple CPUs, increasing CPU execution speed, and increasing the number of I/O attachments.