QoR Assessment Details - 2021.2 English

Vivado Design Suite User Guide: Design Analysis and Closure Techniques (UG906)

Document ID
Release Date
2021.2 English

The QoR Assessment Details table, shown in the following figure, gives a convenient design overview that highlights issues in the following areas that form the basis of the RQA score.

  • Utilization
  • Clocking
  • Congestion
  • Timing
Figure 1. QoR Assessment Details

The table shows design characteristics broken into four categories. Each category is marked OK when there are no sub-items marked REVIEW. When sub-items are marked REVIEW, the failing item is displayed with its threshold and current value. The thresholds are not hard limits and can be exceeded, but going over these limits can make timing closure difficult. Pay particular attention when thresholds are significantly exceeded or when many categories are exceeding their thresholds.

Utilization checks are performed on the whole device, at the SLR level and the Pblock level. Running report_qor_suggestions can help reduce utilization.

Clocking shows whether there is high clock skew on setup or hold paths. Running report_qor_suggestions gives more information on the paths that are impacted by suboptimal clocking, and in some cases can give automated fixes.

Congestion looks into the netlist for profiles that can contribute to routing congestion. Congested region information is not available before placement but some netlist items are available. You might wish to evaluate congestion by running place and route before fixing these items. They do not contribute to the RQA score before the design is placed. Run report_qor_suggestions to generate suggestions that reduce congestion targeted at cells in the congested area.

Timing looks at the 100 worst case paths per clock group. It will look at:
  • WNS, TNS, WHS, and THS to determine whether it is likely the design can close timing.
  • Net budget checks: for routable nets, a conservative net delay is added instead of the estimated delay.
  • LUT budge checks: for LUTs, the delay is swapped for a conservative LUT delay instead of using the estimated delay.

The timing estimates by default give an ideal route estimate when estimating timing. As you progress through the tools, in many cases it is not possible to have every path with ideal routing. LUT and net budget checks allow an estimate that is less than ideal. When paths exceed the slack, these paths should be resolved to reduce the number of issues seen later in the design flow. Generate a CSV file to see more information on these paths.