Save/Restore Handshake Sequencing: Comparison Matrix

Comparison matrix

Retention strategies trade area and complexity against wake reliability and corruption risk.

+------------------+----------------+----------------+----------------+
| Approach         | Strength       | Weakness       | Best when      |
+------------------+----------------+----------------+----------------+
| Strict intent    | high safety    | extra setup    | new designs    |
| Balanced flow    | good velocity  | review overhead | multi-team work |
| Lean checks      | faster runs    | escape risk    | late-cycle triage only |
| Refactor path    | clear contracts | migration cost | legacy cleanup |
+------------------+----------------+----------------+----------------+

When to choose each approach

• Choose LPV posture from escape risk, schedule stage, and owner bandwidth rather than simulator runtime alone.

Interview traps

• Selecting lower-overhead flows without proving corner-case transition behavior.

• Treating waiver volume as closure progress.

Low-power verification deep dive

Retention closure requires proving end-to-end state lifecycle through save, off, and restore windows.

Concept diagram

RETENTION LIFECYCLE

save request -> state capture -> power off -> power on -> restore -> traffic resume

Metric graph

RETENTION STABILITY

restore mismatch       █████
save timing defects    ████
stable wake cycles     ███████

Metrics and artifacts to collect

• retention save/restore timing report

• pre/post state diff matrix

• multi-cycle retention stress summary

• state-loss bug trend by mode

Mini case study

A corruption issue persisted until retention checks compared multi-cycle state snapshots rather than single wake events.

Debug branches

• Track save acknowledgement against actual state capture.

• Validate restore completion before functional traffic resumes.

• Run repeated sleep/wake cycles to expose drift.

Senior review question

Ask: what exact low-power transition boundary failed first, and which artifact proves the closure claim reproducibly?

Key takeaways

• Tie each LPV claim to a concrete transition boundary and one proving artifact.

• Prefer minimal reversible fixes with explicit owner and rollback criteria.

Common pitfalls

• Treating power-aware failures as random before boundary classification.

• Waiving X-prop failures before proving impact and root cause.

• Declaring closure without deterministic replay across key modes.

Principal LPV review addendum

Save/Restore Handshake Sequencing should be reviewed as a transition integrity system, not just isolated checks.

Use Handshake protocol compliance rate, save-to-off and restore-to-functional timing margin, and timeout escape count. as alarm and Temporal handshake checker suite with protocol assertions, timeout diagnostics, and scenario-wise latency histograms. as proof.

Retention closure requires proving save, off, and restore phases as one lifecycle with explicit handshake timing. Closure quality comes from reproducible evidence and explicit owners.