The 3B20D Processor & DMERT Operating System: Overview, Architecture, and Performance of DMERT

The direct predecessor of the 3B20D, the 3A Processor, included a real-time monitor known as the Extended Operating System (EOS). 1 Experience with EOS demonstrated that applications could develop their software with less effort and that synergy resulted between the hardware and software developers. Hence, the hardware is optimized to support the software and the software, in turn, uses the hardware in the most effective manner. The success of EOS led to the decision to support 3B20D applications with a more extensive operating system than EOS. The operating system that resulted is known as the Duplex Multiple Environment Real Time (DMERT) operating system. The basic architecture of D M E R T is based on an earlier system named MERT, 2 which was derived from the UNIX* operating system. 3 Both the UNIX and the M E R T operating systems were origi- * Trademark of Bell Laboratories. 291 nally developed to execute on commercial equipment; today UNIX operating systems are used widely for time-sharing on a variety of computers. The "D" in "DMERT" reflects one of the characteristics that distinguishes it from the previous two operating systems, namely that DMERT is designed to execute on a duplex 3B20 Processor. Thus, the DMERT architecture draws upon concepts from EOS, MERT, and UNIX operating systems. The applications using the 3B20D Processor have been described in detail in a previous article.4 Notice that while different, they have several common characteristics. First, a major component of the application is software.