Primary debug scenario

Symptom: Boot fails at cold temperature (-40C). Passes at room temp. Training log shows narrow read eye at cold.

Triage steps

1. Compare training margins: room temp vs cold vs hot.

2. Check the programmed and trained voltage-reference settings against the selected memory/PHY procedure; do not assume a per-corner table is required without that contract.

3. Compare board and package simulations or measurements with the failing lane and corner.

4. Try increasing training sweep range (if firmware allows).

5. If the sweep cannot find margin, keep board/package loss, power integrity, silicon timing, memory-device behaviour and configuration/training logic as candidates until a controlled change distinguishes them.

Common pitfalls

• Assuming training is one-time for product life.

• Pass/fail without storing margin values.

• Ignoring board vendor differences in training.