Physical-Aware Debug: Expanded Case Study

Extended case study

Closure review: logic-vs-physical delta isolation time, root-cause class distribution regressed after a change touching Physical-Aware Debug.

Background

Team previously had stable baseline across weekly compile runs and agreed guardbands.

Symptoms observed

• logic-vs-physical delta isolation time, root-cause class distribution moved beyond threshold

• Mismatch between local and CI runs

• Owner disagreement on first fix

Investigation timeline

1. Hour 0: freeze manifests and compare run metadata

2. Hour 1: isolate section/topic-specific failure pattern

3. Hour 2: verify constraints and library view consistency

4. Hour 3: inspect transform and mapping deltas

5. Hour 4: choose one reversible fix

6. Hour 5: execute full regression matrix

7. Hour 6: publish closure memo and next actions

Root cause

Root cause centered on Physical-Aware Debug: Physical-aware debug classifies QoR regressions into modeling error, placement pressure, or true logic issues before ECO churn starts.

Fix and validation

• Targeted synthesis tweak with audit trail

• Re-run delta-debug checklist, topo/route compare, ownership board

• Update dashboard and handoff notes

Lessons learned

• Compare like-for-like runs only

• Assign clear owner before ECO

• Keep rollback ready

CASE STUDY — Physical-Aware Debug
baseline / regression / recovery QoR snapshot

Sequence under stress

SYNTHESIS FLOW — Physical-Aware Debug

RTL + constraints
      |
      v
elaboration + checks
      |
      v
mapping + optimization
      |
      v
QoR reports (timing/area/power)
      |
      v
incremental ECO + regression

Primary metric: logic-vs-physical delta isolation time, root-cause class distribution

Synthesis deep dive

Physical-aware synthesis reduces logic-to-route surprise when correlation is monitored.

Concept diagram

PHYSICAL-AWARE LOOP

topo compile -> congestion hints -> handoff -> PD correlation

Metric graph

CORRELATION DELTA

logic view WNS      ███████
topo view WNS       █████
route trial WNS     ████

Reports and artifacts

• topo QoR

• congestion heatmap

• handoff manifest

• delta compare vs PD

Mini case study

Topo compile looked clean, but hotspot congestion predicted route failure and prevented late ECO churn.

Debug branches

• Check hotspot ownership

• Bound correlation drift

• Escalate if handoff assumptions stale

Senior review question

Ask: what evidence proves this QoR move is real and stable?

Key takeaways

• State exact run context (RTL, SDC, libs, switches) with every QoR claim.

• Re-run timing, area, and power regressions after each synthesis ECO.

Common pitfalls

• Comparing runs with mismatched constraints or library views.

• Timing-only fixes that violate power or area budgets.

• Skipping equivalence checks after structural changes.

Principal synthesis review addendum

Physical-aware debug classifies QoR regressions into modeling error, placement pressure, or true logic issues before ECO churn starts.

Metric: logic-vs-physical delta isolation time, root-cause class distribution