Chapter 51 Architecture of the IBM System / 370 i

The years since the introduction of System/360 in 1964 have produced very substantial changes in most aspects of the design, manufacture, and use of information-processing systems. The hardware technology for realizing logic fiinctions has evolved from semi-integrated circuit modules with single devices per chip to hundreds or thousands of circuits on a single silicon chip. The technology for high-speed storage has changed from magnetic cores to dense arrays of transistors on silicon chips. The growth in size and function of systems software has surprised even the practitioners. It is not surprising, therefore, to discover that extensions and refinements to the architecture^ of System/360 were found to be necessary. This paper reviews the motivation for extending the System/360 architecture and describes the design considerations associated with the extensions adopted for System/370.^ It comments on some experiences with the original objectives and concepts of System/360. Finally, it summarizes the characteristics of IBM machines implementing the System/360 and the System/370 architectures [Amdahl, Blaauw, and Brooks, 1964; Amdahl, 1964;