o Increased Wire Length (Detouring): Due to congestion or blockages, detailed router can detour nets. eGR doesn’t detour to report max congestion. This results in difference in earlied net length estimation causing more RC delay and cell delay if more bufs added.
Accurate Parasitic Extraction (RC Extraction): eGR may use tQrc which is fast but less accurate. Detail routing mostly uses iQrc or QRC for extraction which is more accurate resulting in timing degradation.
- Crosstalk Delay: Coupling capacitance between nets switching simultaneously can cause aggressor nets to slow down victim nets (positive crosstalk delay), worsening setup timing. This effect is only accurately calculated post-route.
- Some nets are not being optimized: Run “reportIgnoredNets -outfile filename
- Fixing Antenna detours net and adds load, increasing delay.
- Metal Fill can add couple cap, increasing timing violations.