Technology Mapping: Silicon PPA Impact

Silicon PPA and closure impact

Mapping and buffering choices change congestion and route complexity downstream.

Area drivers

• Buffer growth

• Cell mix shifts

• Retiming duplication

Power drivers

• Leakage from LVT

• Clock power from gating/skew choices

Timing impact

• Critical path depth changes

• Hold/setup coupling

PD consequences

• Congestion ripple

• Handoff predictability

Verification burden

• Equivalence burden

• Regression matrix depth

PPA SNAPSHOT — Technology Mapping
area / dynamic / leakage / WNS / runtime

PPA takeaways

• QoR wins must survive signoff checks

• Correlation beats one-off gains

QoR snapshot

BEFORE / AFTER QOR — Technology Mapping

QoR score
  0 |                     --- target zone
 -1 |        ● regression
 -2 |             ● baseline
 -0.5|                  ● after fix
    +----------------------------------> iteration

Validate timing + area + power, not one number.

Synthesis deep dive

Mapping converts logic intent into real PPA outcomes.

Concept diagram

MAPPING LOOP

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

Metric graph

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

Boolean network mapping selects implementation cells from libraries; mapping choices shape depth, transition behavior, and downstream routability.

Metric: mapped cell count, path delay after mapping, library coverage gaps