Systems & Design

An Analysis Of Blocking Vs. Non-Blocking Flow Control In On-Chip Networks

A look at ways to minimize latency of priority traffic and jitter compared with a single-threaded tag-based protocol approach.


High end System-on-Chip (SoC) architectures consist of tens of processing engines. These processing engines have varied traffic profiles consisting of priority traffic that require that the latency of the traffic is minimized, controlled bandwidth traffic that require low service jitter on the throughput, and best effort traffic that can tolerate highly variable service. In this paper, we investigate the trade-off between multi-threaded non-blocking (MTNB) flow-control and single threaded tag (STT) based flow-control in the realm of Open Core Protocol (OCP) [1] specifications. Specifically, we argue that the non-blocking multi-threaded flow-control protocol is more suitable for latency minimization of the priority traffic and jitter minimization of controlled bandwidth traffic, when compared with a single threaded tag (STT) based protocol. We present experimental results comparing MTNB against STT based protocols on representative DTV data flows. On average, in the STT based system, the latency of priority traffic is increased by 2.73 times and the latency of controlled bandwidth traffic is increased by 1.14 times when compared to the MTNB system, under identical configurations.

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