Extending a CPU Design Project to Reinforce Learning

A computer systems course using the "Nand2Tetris" materials has been taught in our institution for two years. Assignment work is based around extensions or variations of the projects provided. The challenge described in this paper was to develop a variation of project 5 that supported student's authentic learning of basic CPU design within time constrains and fitted with existing course materials. A 2-phase CPU design assignment was created that asked students to complete first the CPU design from the text book, and then complete an alternative CPU which replaced the D-register with a small register bank; each phase was weighted equally. The second phase reinforced the concepts learned in the first phase by making students identify the significant overlaps when decoding and generating control bits, as well as being exposed to hardware design choices at register level. Note files for project 5 can be easily sourced from MOOC resources, while this is not the case for the second phase as this was our own CPU design. Other alternative designs are possible, which can be used in rotation for this course. We could also ask students in advance CA courses to design and code their own extension of the Hack machine.