Chapter 2 - HPC Architecture 1: Systems and Technologies

Abstract

Computer architecture is the organization of the components making up a computer system and the semantics or meaning of the operations that guide its function. As such, the computer architecture governs the design of a family of computers and defines the logical interface that is targeted by programming languages and their compilers. The organization determines the mix of functional units of which the system is composed and the structure of their interconnectivity. The architecture semantics is the meaning of what the systems do under user direction and how their functional units are controlled to work together. An important embodiment of semantics is the instruction set architecture (ISA) of the system. The ISA is a logical (usually binary) representative encoding of the basic set of distinct operations that a computer architecture may perform, and by which application programs specify the useful work to be done. At the machine level the hardware (sometimes controlled by firmware) system directly interprets and executes a sequence or partially ordered set of these basic operations. This is true for all computer cores, from those few in the smallest mobile phones to potentially millions making up the world's largest supercomputers. High performance computer architecture extends structure to a hierarchy of functional elements, whether small and limited in capability or possibly entire processor cores themselves. In this chapter many different classes of structure are presented, each exploiting concurrency in its own particular way. But in all cases this more broad definition of general architecture for high performance computing emphasizes aspects of the system that contribute to achieving performance. A high performance computer is designed to go fast, and its organization and semantics are specially devised to deliver computational speed. This chapter introduces the basic foundations of computer architecture in general and for high performance computer systems in particular. It is here, at the structural and logical levels, that parallelism of operation in its many forms and size is first presented. This chapter provides a first examination of the principal forms of supercomputer architecture and the underlying concepts that govern their performance.