Crosstalk / signal integrity timing analysis

[robtaylor]

Summary

Model crosstalk-induced delay changes from coupling capacitance between adjacent wires.

Current State

GEM uses only nominal wire delays from SDF INTERCONNECT. Adjacent signal switching can add or subtract delay (crosstalk speedup/slowdown) by 10-20%.

Proposed Approach

• Would require SPEF with coupling capacitance data (not just lumped parasitics)
• Compute crosstalk delta delays based on aggressor/victim switching patterns
• Add crosstalk pessimism to timing checks
• Detect potential glitch conditions on quiet nets

Impact

Low-Medium — important for advanced nodes but less critical for sky130.

Effort

Very High — needs coupling data from extraction, aggressor analysis, and complex delay computation. Essentially reimplementing PrimeTime SI.

Notes

This is a long-term goal. For sky130 at moderate frequencies, crosstalk effects are small. More relevant for advanced nodes with tighter spacing.