Comparison of channel protocols for low latency, low energy communication over transmission lines

The eminence of communication costs over computation costs in current systems-on-chip (SoCs) has led to a change in the assumptions and methodology of the deep submicron design process. The emergence of non-traditional global signaling techniques such as optical interconnects, wireless communication, and transmission lines adds further complexity to the design exercise. There is a pressing need for a better understanding of communication overheads, especially in long links. Previous research has been performed that mathematically models various synchronous and asynchronous pipeline protocols for long diffusive wires. The work presented in this paper adapts these throughput, latency, and energy models for fast, low power communication over on-chip transmission line interconnects. Using common parameters and metrics to characterize the channel protocols enables analogous comparisons among them. First order models are created and populated with SPICE values to collate performance metrics for global channels. The paper then compares the behavior of transmission lines and diffusive wires under these signaling protocols. Finally, the effect of wire length on channel performance is studied.