Visible to Intel only — GUID: oot1591093470184
Ixiasoft
Tension and Span Rules
The tension and span rules help identify areas of the design that may be difficult for the fitter to place, even if they are meeting timing.
These rules identify registers with sinks that are pulling it in various directions, making it difficult to find an optimal placement.
Registers that fail these rules are good candidates for register duplication. They are low priority rules. Your design can still be meeting timing even if these rules are violating, but they help identify the areas of the design that can contribute to congestion. When looking for places for further optimization, these are good candidates.
Figure 23. TensionTension is the sum over each sink (either immediate fanout or timing endpoint, depending on the rule) of the distance of the sink from the centroid of all the sinks.
Figure 24. Span Span is the maximum one-dimensional delta between the left-bottom-most sink with the right-top-most sink.
The rules are:
- TMC-20601 – Registers with High Fan-out Tension
- TMC-20602 – Registers with High Endpoint Tension
- TMC-20603 – Registers with High Fan-out Span
- TMC-20604 – Registers with High Endpoint Span
Duplicating these signals where possible allows Quartus® Prime to find a better solution.
Figure 25. High Tension Fanout Signal
