FinalReport - A Reversible M68HC11 Simulator and Its...

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A Reversible M68HC11 Simulator and Its Empirical Computational Complexity Charles A. Vermette, Jr. CIS 4914 Senior Project Advisor: Dr. Michael P. Frank ( mpf@cise.ufl.edu ) Date of Talk: August 7, 2001
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Abstract: This project was done to empirically evaluate the space/time complexity of C. H. Bennett’s 1989 algorithm for reversibly simulating irreversible programs. Such an analysis is desirable because, although there has been mathematical discussion over this method of simulation, there has not been hard evidence gathered from a real irreversible machine being simulated on a real reversible machine. This project was to simulate a common real-world architecture, the Motorola M68HC11, using PISA code designed for a prototype Pendulum reversible microprocessor. The PISA program had to be simulated since the prototype chip contained a bug and because it would be easier to gather the space/time measurements from the simulated environment. The project was not successfully completed. R language to PISA compiler malfunctions, as well as overruns in simulator design and implementation, cut off the time required for gathering the complexity information. The project was not a total loss, however. The simulator code was complete enough to run a test program, although the code can’t be compiled or debugged yet, using a simplified version of the simulation method. As the largest R program to date, it exposed problems in the compiler and also provided supporting arguments for developing new language constructs. Introduction: The field of reversible computing is under research because it may lead to more efficient means of computation. Current irreversible computational models ignore the fundamentally reversible nature of the physical world in favor of more abstract mathematical models of computation. This lack of concern with the underlying physical realities leads to a large increase in the rate of release of thermal entropy in these systems over the amount required by physics [5]. This entropy is expressed in heat [3, p. 48], which must be channeled away from the device to avoid damaging it. Reversible computers hold the promise of reducing the outward flow rate of entropy, resulting in more efficient machines and ultimately allowing computer technology to push towards the physical limits it is capable of [3, p. 143]. However, programming models with which most people are familiar are based on the irreversible computing systems currently in use. This means existing languages - such as 2
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C, C++, Pascal, etc. - have many irreversible notions embedded into them - like assignment statements, flow control “jumps”, and so on - that do not lend themselves directly to reversible models of computation [2]. It is therefore of interest to develop methods of simulating these irreversible programming constructs with reversible code, so that existing code bases and programmers can be used with the new reversible machines. In the end most code should be converted over to natively reversible algorithms, but
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This note was uploaded on 01/20/2012 for the course CIS 4914 taught by Professor Desimone during the Spring '08 term at University of Florida.

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FinalReport - A Reversible M68HC11 Simulator and Its...

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