The 1940s are remembered in electronic history for the invention of the transistor, and the 1950s for the invention of the integrated circuit. As the millennium comes to a close, another major development in the world of electronic design has come to the forefront: the ability to integrate an entire "system" onto a single computer chip. System-on-a-chip (SOC) designs have been in existence for only a few years; however, in that span of time, the definition of the "system" designed and manufactured on a chip has significantly changed and expanded as did the technology, skills, tools and methodologies required to produce it. This paper examines the changing characteristics of SOC design, from the mid 1990s when there was a limited number of processor-based in-house designs, to the present-day definition which includes multiple processors, peripherals, communication subsystems, bus hierarchies, analog components, and radio frequency (RF). The increasing levels of SOC integration will be illustrated by a family of set-top box designs.
