Priority division: A high-speed shared-memory bus arbitration with bounded latency

Hardik Shah, Andreas Raabe, Alois C. Knoll

Abstract: In state-of-the-art multi-processor systems-on-chip (MPSoC), interconnect of processing elements has a major impact on the system's overall average-case and worst-case performance. Moreover, in real-time applications predictability of inter-chip communication latency is imperative for bounding the response time of the overall system. In shared-memory MPSoCs buses are still the prevalent means of on-chip communication for small to medium size chip-multi-processors (CMPs). Still, bus arbitration schemes employed in current architectures either deliver good average-case performance (i.e. maximize bus utilization) or enable tight bounding of worst-case-execution time. This paper presents a shared bus arbitration approach allowing high bus utilization while guaranteeing a fixed bandwidth per time frame to each master. Thus it provides high-performance to both realtime and any-time applications or even a mixture of both. The paper includes performance results obtained while executing random traffic on a shared bus implemented on a FPGA. The results show that our approach provides bus utilization close to static priority based arbitration, a fairer bandwidth distribution than Round Robin and latency guarantees identical to TDMA. With this it combines the best properties of these schemes.