Computer Design Experiments

After writing a simulator of an Unlimited Register Machine (Shepherdson, Sturgis 1963) in Python, I thought it might be cool to realize a finite version of the machine using logic gates. That's what I intend to share here for now: a simulation of URM in Logisim.

I've tried two architectures: Harvard (separate ROM and RAM) and von Neumann (shared RAM). Pictures of the high-level design (the wires are hidden through ports) follow.

Harvard Architecture

Von Neumann Architecture

Next steps

• share the components and their descriptions
• share the actual logisim files
• realize the machine in an FPGA
• realize the machine using 7400/4000-type logic gates

Tools

• Logisim

References

• Cutland, N.J. (1980) Computability: An Introduction to Recursive Function Theory.
• Shepherdson, J.C., Sturgis, H.E. (1963) Computability of Recursive Functions