A simulated system for teaching

The evolution of computers has led to the current generation of powerful, RISC-based workstations. These systems are often rich of interesting architectural features and peripheral devices. Very often, they also run multitasking, multiuser operating systems which make almost complete use of the available hardware. This makes it very hard to use these systems for the lab classes of a computer architecture course, to show how to deal with peripherals and mechanisms such as interrupt and memory protection. In fact, working on these subjects almost unavoidably means breaking, thus loosing, a lot of the support provided by the operating system, not to mention the possibility of wiping out data from the storage devices. In order to overcome these diiculties, and to be able to support the teaching of computer architecture with signiicant experiments in a controlled environment, we have developed a simulated computer system running under Unix. The simulated system consists of CPU, memory and its peripherals, and has a complete interrupt mechanism which permits the study of advanced techniques for peripheral management and other operating system's issues. The simulator runs on a variety of Unix platforms, both with and without a windowing system. The paper describes the architecture of the system and shows some examples of its use.