Half-buffer retiming and token cages for synchronous elastic circuits

Synchronous elastic circuits borrow the tolerance of computation and communication latencies from the asynchronous design style. The datapath is made elastic by turning registers into elastic buffers and adding a control layer that uses synchronous handshake signals and join/fork controllers. Join elements are the objective of two improvements discussed in this paper. Half-buffer retiming allows the creation of input queues by relocating one of the latches of the elastic buffer which follows the join controller. Token cages improve the performance of join controllers that use the early evaluation firing rule. Their effect on throughput is discussed by means of examples representative of typical topologies, simulations with synthetic benchmarks and a realistic microarchitecture. Area and power costs of the control logic and the possible impact on the datapath are evaluated, based on the results of logic synthesis experiments on a 45 nm CMOS technology. Index Terms Elastic circuits, Latency tolerance.