Real-time wormhole channels

A method for calculating hard QoS guarantees for Networks-on-Chip

“…Therefore, we also calculate a minimum permitted interval (mIi) between two consecutive packets from the same source, which can be translated into a maximum permitted bandwidth ( MBWi). This approach is similar to previously published method [10] (Real-time wormhole channel feasibility checking or WCFC, which will be briefly described later), but delivers substantially better results in terms of bound tightness. For proper operation, the system must then respect MBWi bounds at runtime.…”

“…To be consistent with the notations from [10] and for convenience, we introduce the uppercase Ui j symbol, which models the hop delay from output buffer to output buffer, instead of from input buffer to input buffer.…”

“…This method, called RTB-LL (Real-Time Bound for Low-Latency traffic) requires a very simple traffic regulation at network injection points. RTB-LL is a significant improvement to the WCFC bound proposed in [10], while RBT-HB is completely new. Table 1 summarizes a cross-comparison of RTB-HB, RTB-LL and WCFC methods.…”

“…We then formulate algorithms to find conservative latency and bandwidth bounds on end-to-end traffic flows transported by a best-effort wormhole NoC fabric with no special hardware support for RT traffic. Our approach is inspired by the work by Lee et al [10] for traditional multiprocessor networks, which we extend in several directions.…”

Improving Performance Guarantees in Wormhole Mesh NoC Designs

“…In [12], [21] authors provide realistic bounds for wNoCs without using flit-level virtual channel preemption. The model in [21] requires knowing all communication flows integrated in the system to derive safe upper-bounds, making those bounds not time-composable.…”