A Negative-Overhead, Self-Timed Pipeline

This paper presents a novel variation of wave pipelining that we call “surfing.” In previous wave pipelined designs, timing uncertainty grows monotonically as events propagate through gates or other logic elements. We bound this dispersion by propagating a timing pulse along with the data values. Our logic elements have delays that are smaller in the presence of the pulse than in its absence. This produces a “surfing” effect: events are bound in close proximity to the timing pulse. We demonstrate this approach with the design of a 4 12 multiplier. Spice simulations from the extracted layout indicate that this design is robust in the presence of fabrication parameter variation and power supply noise. Because timing is maintained by accelerating the logic, our designs achieve lower latency than their purely combinational equivalents. Thus, the control overhead for these designs is indeed negative. Appeared in Proceedings of Eighth International Symposium on Advanced Research in Asynchronous Circuits and Systems, April 2002.