Synthesis & Logic Optimization · All levels

Structuring & Buffering: Step-by-Step Walkthrough

Step-by-Step Walkthrough for Structuring & Buffering.

Step-by-step analysis walkthrough

Use when you own Structuring & Buffering in a synthesis closure review.

Confirm exact run context (RTL/SDC/lib/switch set).
Open section QoR dashboard and identify first drift.
Inspect topic-level report for mechanism evidence.
Determine owner and candidate reversible action.
Apply one change only; avoid bundled fixes.
Run full timing/area/power checks.
Validate side effects on neighboring path groups.
Publish memo with outcome and residual risk.

Artifacts to collect

fanout report, transition report, structure diff
QoR dashboard
run manifest
constraint diff
regression matrix

Decision memo template

diagram

SYNTHESIS DECISION MEMO — Structuring & Buffering
run context:
observed metric:
hypothesis:
fix:
regression:
owners: synthesis owner, PD owner, STA owner

Reference visuals

Structure vs buffer tradeoff

diagram

critical cone
  |-- restructure logic (depth)
  |-- add buffers (fanout/slew)

Choose by dominant delay mode.

Synthesis deep dive

Mapping converts logic intent into real PPA outcomes.

Concept diagram

diagram

MAPPING LOOP

boolean net -> library mapping -> optimization -> report and iterate

Metric graph

diagram

MAPPING IMPACT

depth reduction   ███████
fanout cleanup    █████
runtime overhead  ███

Reports and artifacts

mapping summary
critical path cell list
fanout/slew report
library coverage

Mini case study

Cell-heavy critical path improved after restructuring, while blanket buffering had worsened power.

Debug branches

Depth issue -> structure
Fanout issue -> buffers
Library mismatch -> view audit

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

Structuring rewrites logic cones and buffering controls transition/fanout; both directly affect timing, area, and power in different corners.

Metric: logic depth, fanout violations, buffer count, slew violations

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