Illustrating CPU design concepts with DLSim 3

DLSim, a GUI-based digital logic simulation program developed by Richard Salter at Oberlin College, has been used for class demonstrations and homework exercises in the Computer Organization course at Oberlin for over ten years. Until recently its use has been limited to the component of the course dealing with low-level logic design using gates and flip-flops. A new version, DLSim 3, extends those capabilities through the use of Java plug-ins, making it possible to use the software for digital design at higher levels of abstraction. With DLSim 3, we are able to present the many levels of circuit design in a single environment, from low level combinational and sequential circuits through models of complete CPUs. The purpose of this paper is to give an introduction to DLSim 3 and to describe how we have used it in the classroom, focusing particularly on CPU design.