A number of investigators have continued to discuss application of asynchronous techniques to improve the computational power of computing systems. 2 , 12 , 5 , 9 In fact the need for asynchronous design techniques arose in the earliest machines 26 , 20 , 6 which introduced parallel handling of bits in a number and overlapping of independent operations. The concept of distributed autonomous concurrent processors was essential to the visionary architecture proposed by Holland 16 to support "operating programs floating in a sea of hardware." The importance of such concurrent and asynchronous systems has increased recently because of the availability of entire processing units on one or a few chips and the potential cost reduction of those units. Moreover, it is expected that work on VLSI technology will permit even more complex systems to be reduced to silicon if their design and market analysis have been validated sufficiently to justify the cost. The need for validation prior to costly physical implementation has increased the value of methods and tools which support modeling and analysis.