Building and Reading Shmoo Plots: Reports and Metrics

Reports and metrics

Reports and Metrics for Building and Reading Shmoo Plots is anchored on Shmoo completeness score (axis coverage and step resolution), rerun reproducibility, and fail-cluster density per sweep window.. Convert observed behavior into mechanism-backed and owner-bound actions.

A useful report explains why behavior moved, not only that behavior moved.

Evidence matrix

EVIDENCE MATRIX - Building and Reading Shmoo Plots

+-------------------------------+--------------------------------+--------------------------------+-----------------------------+
| Evidence                      | Tells you                      | Does not prove                 | Next action                 |
+-------------------------------+--------------------------------+--------------------------------+-----------------------------+
| rail/current timeline         | sequencing and power health    | firmware or protocol integrity | align with stage logs       |
| stage checkpoint logs         | failing transition boundary    | electrical root cause          | correlate with scope traces |
| interface trace/decode        | protocol behavior and timing   | global platform readiness      | replay under fixed setup    |
| shmoo/corner matrix           | margin-sensitive fail region   | exact failing mechanism        | isolate with targeted tests |
| before/after replay packet    | mitigation movement quality    | long-run stability             | run soak and corner matrix  |
+-------------------------------+--------------------------------+--------------------------------+-----------------------------+

• Track Shmoo completeness score (axis coverage and step resolution), rerun reproducibility, and fail-cluster density per sweep window. on representative board and corner slices.

• Include board/firmware/corner metadata in every report header.

• Correlate electrical, software, and protocol evidence in one timeline.

• Call out contradictory evidence explicitly.

Silicon bring-up deep dive

Characterization creates release confidence only when sweep design and fail signatures remain stable across reruns.

Concept diagram

CHARACTERIZATION WORKFLOW

sweep plan -> capture matrix -> isolate edges -> define guardband -> validate

Metric graph

SHMOO SIGNAL QUALITY

isolated holes           ████
stable fail clusters     ███████
validated guardbands     ██████

Metrics and artifacts to collect

• pass-island continuity map

• corner fail-cluster density

• guardband recommendation log

• retest reproducibility ratio

Mini case study

A nominal-corner shmoo hole was explained after separating true timing margin loss from fixture sensitivity effects.

Debug branches

• Match setup state before comparing corner points.

• Classify fail clusters by signature, not just count.

• Validate guardbands with independent replay runs.

Senior review question

Ask: what is the first failing boundary, which artifact proves it, and who owns bounded closure?

Key takeaways

• Tie every bring-up claim to one reproducible setup state and one proving artifact.

• Prefer bounded fixes with clear owner and rollback trigger over broad multi-variable edits.

Common pitfalls

• Running parallel uncontrolled experiments and losing causality.

• Declaring closure without replaying across representative corners.

• Escalating severity before bench/setup hypotheses are disproven.

Report interpretation

Interpret movement only when setup metadata is matched.

A useful report isolates first-failure stage and disqualifies alternate causes.