Energy-efficient Pipeline Templates for High Performance Asynchronous Circuits

Basit Riaz Sheikh and Rajit Manohar

We present two novel energy-efficient pipeline templates for high throughput asynchronous circuits. The proposed templates, called N-P and N-Inverter pipelines, use a single-track handshake protocol. There are multiple stages of logic within each pipeline. The handshake overhead is greatly minimized by eliminating explicit validity and neutrality detection gates for input tokens and intermediate logic nodes. Each template can pack significant amount of logic in a single stage, while still maintaining a fast cycle time of only 18 transitions. Noise and timing robustness constraints of our pipelined circuits are quantified across all process corners. A completion detection scheme based on wide NOR gates is presented, which results in significant latency and energy savings especially as the number of outputs increase. To fully quantify all design trade-offs, three separate pipeline implementations of an 8x8-bit booth-encoded array multiplier are presented. Compared to a standard QDI pipeline implementation, the N-Inverter and N-P pipeline implementations reduced the energy-delay product by 38.5% and 44% respectively. The overall multiplier latency was reduced by 20.2% and 18.7%, while the total transistor count was reduced by 42.2% and 54.3% with N-Inverter and N-P pipeline templates respectively.