The cost of using the CAP computer's protection facilities

The CAP project was set up as an experiment in hardware memory protection. The aim of the project was to design and build a computer with very detailed memory protection, one of the objectives being that the design should facilitate the development of an operating system. The computer has been built and an operating system written which exploits its powerful protection facilities. An overview of the project is given in [3] and the basic architecture is described in [4].