LIBRARIES Reversible Computer Engineering and Architecture by

There exists a set of reversible primitive modules that may be combined according to a set of simple rules to create larger systems, which are themselves reversible primitive modules. These modules may be combined to create a fully reversible, universal computer. I describe techniques for creating reversible primitive modules from simple switches, such as conventional CMOS transistors, and the rules for combining these modules to maintain re-versibility. As an example of a complex system that can be constructed from these modules, a fully reversible microprocessor, Pendulum, is presented. This universal microprocessor has been fabricated in a 0.5 pm CMOS process and tested. Pendulum has eighteen instructions, including memory access, branching instructions, and direction changing instructions. The datapath supports twelve-bit wide data and address values. The motivation for reversible computing research comes from an investigation of funda-mental limits of energy dissipation during computation. A minimum energy dissipation of kBT ln 2, where kB is Boltzmann's constant, is required when a bit is erased. Erasing a bit is a logically irreversible operation with a physically irreversible effect. A reversible compute