The development of the next generation of computer systems is characterized
mainly by the acceptance of parallel processing. Until this time parallelism was limited
to pipelining and vector processing, or at most to a few processors sharing jobs. The
fifth generation saw the introduction of machines with hundreds of processors that could
all
be working on different parts of a single program. The scale of
integration in semiconductors continued at an incredible pace
--- by 1990 it was possible to build chips with a million
components --- and semiconductor memories became standard
on all computers.
Other new developments were the widespread use of computer networks and the increasing use of single-user workstations. Prior to 1985 large scale parallel processing was viewed as a research goal, but two systems introduced around this time are typical of the first commercial products to be based on parallel processing. The Sequent Balance 8000 connected up to 20 processors to a single shared memory module (but each processor had its own local cache). The machine was designed to compete with the DEC VAX--780 as a general purpose Unix system, with each processor working on a different user's job. However Sequent provided a library of subroutines that would allow programmers to write programs that would use more than one processor, and the machine was widely used to explore parallel algorithms and programming techniques.
