25 Years Ago: the First Asynchronous Microprocessor

Twenty-five years ago, in December 1988, my research group at Caltech submitted the world’s first asynchronous (“clockless”) microprocessor design for fabrication to MOSIS. We received the chips in early 1989; testing started in February 1989. The chips were found fully functional on first silicon. The results were presented at the Decennial Caltech VLSI Conference in March of the same year. The first entirely asynchronous microprocessor had been designed and successfully fabricated. As the technology finally reaches industry, and with the benefit of a quarter-century hindsight, here is a recollection of this landmark project.