MicMac: a microprogram simulator for courses in computer organization

The subject of microprogramming should be an important part of a course in computer organization. It connects the higher-level view of the machine (machine language, instruction set, register and memory architecture) with the lower-level view (digital logic), by showing how an instruction set can be implemented using digital logic. Unfortunately, there are several obstacles in the way of a suitable presentation of microprogramming in an undergraduate course. One is that detailed specifications of the microprogramming level of currently popular computers are considered to be proprietary information and for that reason are usually unavailable. When such specifications are available, they are typically of such a complex nature as to make then unsuitable as an introduction to the subject of microprogramming for beginning students. Another problem is the lack of proper facilities for laboratory work in microprogramming. Although microprogrammable processors, such as the Burroughs B1830, do exist and have been used in teaching computer organization [2], most colleges and universities do not have access to such machines.