The Design of High-Performance Dynamic Asynchronous Pipelines: High-Capacity Style

Abstract

This paper introduces a high-throughput asynchronous pipeline style, called high-capacity (HC) pipelines, targeted to datapaths that use dynamic logic. This approach includes a novel highly-concurrent handshake protocol, with fewer synchronization points between neighboring pipeline stages than almost all existing asynchronous dynamic pipelining approaches. Furthermore, the dynamic pipelines provide 100% buffering capacity, without explicit latches, by means of separate pullup and pulldown control for each pipeline stage: neighboring stages can store distinct data items, unlike almost all existing latchless dynamic asynchronous pipelines. As a result, very high throughput is obtained. Fabricated first-input-first-output (FIFO) designs, in 0.18-m technology, were fully functional over a wide range of supply voltages (1.2 to over 2.5 V), exhibiting a corresponding range of throughputs from 1.0-2.4 giga items/s. In addition, an experimental finite-impulse response (FIR) filter chip was designed and fabricated with IBM Research, whose speed-critical core used an HC pipeline. The HC pipeline exhibited throughputs up to 1.8 giga items/s, and the overall filter achieved 1.32 giga items/s, thus obtaining 15% higher throughput and 50% lower latency than the fastest previously-reported synchronous FIR filter, also designed at IBM Research.