Published on Dec 06, 2015
Over the past four decades the computer industry has experienced four generations of development, physically marked by the rapid changing of building blocks from relays and vacuum tubes (1940-1950s) to discrete diodes and transistors (1950-1960s), to small- and medium-scale integrated (SSI/MSI) circuits (1960-1970s), and to large- and very-large-scale integrated (LSI/VLSI) devices (1970s and beyond).
Increases in device speed and reliability and reductions in hardware cost and physical size have greatly enhanced computer performance. However, better devices are not the sole factor contributing to high performance.
Ever since the stored-program concept of von Neumann, the computer has been recognized as more than just a hardware organization problem. A modern computer system is really a composite of such items as processors, memories, functional units, interconnection networks, compilers, operating systems, peripherals devices, communication channels, and database banks.
To design a powerful and cost-effective computer system and to devise efficient programs to solve a computational problem, one must understand the underlying hardware and software system structures and the computing algorithm to be implemented on the machine with some user-oriented programming languages. These disciplines constitute the technical scope of computer architecture.
Computer architecture is really a system concept integrating hardware, software algorithms, and languages to perform large computations. A good computer architect should master all these disciplines. It is the revolutionary advances in integrated circuits and system architecture that have contributed most to the significant improvement of computer performance during the past 40 years. In this section, we review the generations of computer systems and indicate the general tends in the development of high performance computers.
The division of computer systems into generations is determined by the device technology, system architecture, processing mode, and languages used. We consider each generation to have a time span of about 10 years. Adjacent generations may overlap in several years as demonstrated in the figure. The long time span is intended to cover both development and use of the machines in various parts of the world. We are currently in the fourth generation, while the fifth generation is not materialized yet.
Computers to be used in the 1990s may be the next generation. Very large-scale integrated (VLSI) chips will be used along with high-density modular design. Multiprocessors like the 16 processors in the S-1 project at Lawrence Livermore National Laboratory and in the Denelcor's HEP will be required. Cray-2 is expected to have four processors, to be delivered in 1985. More than 1000 mega float-point operations per second (megaflops) are expected in these future supercomputers.
Achieving high performance depends not only on using faster and more reliable hardware devices, but also on major improvements in computer architecture and processing techniques. State - of - the art parallel computer systems can be characterized into three structural classes: pipelined computers, array processors and multi-processor systems. Parallel processing computers provide a cost-effective means to achieve high system performance through concurrent activities.