Improving NoC Performance by Optimizing NoC QoS Over Fabric Timing QoR - 2025.2 English - UG1388

When end-to-end quality of service (QoS) differs between the NoC implementation before and after place_design, this might be due to placement differences for the NoC solution. Before place_design, the NoC placement is determined without the placement of the rest of the design. Therefore, the NoC compiler can use the optimal locations for NMUs and NSUs to achieve the maximum bandwidth. During the implementation flow, the Vivado placer tries to balance the NoC QoS requirements and the fabric timing QoR.

In some cases, this can result in the NoC compiler creating a suboptimal solution for QoS. If QoS degrades during place_design and does not meet the pre-place QoS, you can try place_design with the -no_noc_opt option to use the pre-place NoC compiler solution as an anchor for the rest of the logic. This might result in timing closure challenges for logic that interfaces to the NoC but should meet the original NoC QOS results.

CRITICAL WARNING: [Ipconfig 75-4216] A NoC solution that meets the requested bandwidths could not be found. The following solution relaxes bandwidth requirements.