Designing Control Logic for Counterflow Pipeline Processor Using Petri Nets
Formal Methods in System Design
On the Correctness of the Sproull Counterflow Pipeline Processor
ASYNC '96 Proceedings of the 2nd International Symposium on Advanced Research in Asynchronous Circuits and Systems
A Counterflow Pipeline Experiment
ASYNC '99 Proceedings of the 5th International Symposium on Advanced Research in Asynchronous Circuits and Systems
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Much design effort toward a Sproull Counterflow Pipeline Processor has been focused on management of movements of Instructions and Results in the pipelines so that every Instruction and Result that pass one another meet and interact in exactly one stage of the pipeline. The full SCPP design problem poses other requirements as well, such as creation and deletion of items flowing in the pipelines, scheduling of execution of instructions only in stages with the required hardware, and high speed. Nevertheless, even a simplified version of the design problem that ignores the latter requirements has resisted synthesis using existing formal methods. At a workshop on Asynchronous VLSI Design held in Israel on March 20-22, 1995, Alain Martin of Caltech discussed his synthesis methodology and tools, which he claimed can translate almost any Communicating Sequential Process (CSP) program to a circuit by systematic procedure. Since our essential requirements for movement of Instructions and Results had been expressed by us as a 5-state FSM graph that is easily interpreted as a CSP program, we asked Martin to demonstrate how his method would be applied to this problem. At the suggestion of the workshop organizer, Dr. Ran Ginosar of the Technion, Dr. Huub Schols presented the challenge to all of the workshop attendees, and produced the careful documentation contained here. Several thoughtful responses to our challenge are cited in the list of references. They lead us to conclude that the problem that we have posed is indeed difficult and worthy of further study and analysis. Martin has declined to provide us with any information about a solution that he claimed to have found after the workshop.