This paper describes a visualization environment and associated learning activities designed to improve learning of computer architecture. The environment, EasyCPU, displays a model of the components of a computer and the dynamic processes involved in program execution. We present the results of a research program that analysed the contribution of the visualization to learning. We found that EasyCPU facilitated the use of improved study methods and enabled the construction of a viable mental model of the computer. (Contains 2 figures and 2 tables.)