Verkar spännande att ha till hands om man vill lära sig hur det fungerar.CPU Sim is a Java application that I wrote that allows users to design simple computer CPU's at the microcode level and to run machine-language or assembly-language programs on those CPU's through simulation. It can be used to simulate a variety of architectures, including accumulator-based, RISC-like, or stack-based (such as the JVM) architectures.
http://www.cs.colby.edu/djskrien/CPUSim/