XA I/O ARCHITECTURE TUTORIAL.

The basic System/370 channel architecture had served well, and more or less unaltered, since the introduction of the System/360 in 1964. But by the mid 70s it was becoming apparent that enhancements were desirable to better handle the trend to multiprocessors and the increasing gap between the speed of processors and peripherals. This paper starts therefore by reviewing the System/370 I/O architecture, and then looks at the enhancements in 370-XA.