CPU 101: Design of a Simple Microprocessor from First Principles

Microprocessors are the central elements of modern computing systems and understanding their design principles is crucial for the progression of the compute continuum. This paper describes the design of a simple 8-bit microprocessor from the basics, and sheds light on a gradual approach that addresses the different phases of CPU design and how one addresses the issues that one typically encounters in the process. It describes all the phases starting from how decisions are made about the ISA, the features, the scope of the work etc; all of which establish the groundwork for the subsequent design choices. It is believed that this paper will be of use especially to the student community. The work provides an enlightening perspective into the realm of microprocessor designing and its hands-on realization, delivering a deep understanding of the steps involved in designing the core of computing systems.