Latency and throughput tradeoffs in self-timed speed-independent pipelines and rings

Asynchronous pipelines control the flow of tokens through a sequence of logical stages based on the status of local completion detectors. As in a synchronously clocked circuit, the design of self-timed pipelines can trade off between achieving low latency and high throughput. However, there are more degrees of freedom because of the variances in specific latch and function block styles, and the possibility of varying both the number of latches between function blocks and their connections to the completion detectors. This report demonstrates the utility of a graph-based methodology for analyzing the timing dependencies and uses it to make comparisons of different configurations. It is shown that the extremes for high throughput and low latency differ significantly, the placement of the completion detectors influences timing as much as adding an additional latch, and the choice as to whether precharged or static logic is best is dependent on the cost in complexity of the completion detectors.