Interview drills

Interview Drills for Interrupt Topology Contracts focuses on interrupt latency tail, missed-interrupt incidents. The goal is to map symptoms to boundary contracts, owner actions, and regression-proof closure.

PROMPT
You observe interrupt latency tail, missed-interrupt incidents in Interrupt Topology Contracts. Explain root cause and closure plan.

STRONG ANSWER
1. Names baseline manifest and failing boundary.
2. Explains Interrupt architecture defines aggregation, priority, routing, and affinity policies that software relies on for deterministic response.
3. Requests interrupt topology diagram, latency trace, affinity policy sheet.
4. Proposes minimal reversible fix + full regression scope.

WEAK ANSWER
Suggests broad optimizations or owner blame without baseline and artifact evidence.

Diagram to draw on whiteboard

Interrupt topology

INTERRUPT TOPOLOGY

peripherals -> local aggregators -> global controller -> CPU targets
                       |
                priority + affinity policy

Root-cause tree to narrate

ROOT-CAUSE TREE — Interrupt Topology Contracts

interrupt latency tail, missed-interrupt incidents regressed
         |
   same baseline manifest?
      /           \
    no             yes
    |               |
version/collateral  real integration
mismatch            contract break
 /       \            |
inputs    env      isolate domain
drift     drift    and first failure

SoC deep dive

Address, interrupt, and IO contracts are where hardware/software alignment is won or lost.

Concept diagram

HW/SW CONTRACT
address map + interrupt model + io defaults -> firmware behavior

Metric graph

BOOT REGRESSION SOURCES
map churn █████
reset defaults ████
driver mismatch ███

Reports and artifacts

• address decode audit

• interrupt latency report

• IO bring-up checklist

• boot contract review

Mini case study

A map alias issue caused sporadic peripheral misconfiguration despite clean block-level tests.

Debug branches

• Freeze address map baseline

• Audit reset defaults

• Validate firmware assumptions

Senior review question

Ask: what baseline, owner, and artifact prove this topic is truly closed?

Key takeaways

• State baseline manifest and owner with every closure metric.

• Run cross-domain regression after every top-level fix.

Common pitfalls

• Comparing results across different manifests.

• Unowned issues slipping through review cycles.

• Waiving risks without expiry and validation plan.

Principal SoC review addendum

Interrupt architecture defines aggregation, priority, routing, and affinity policies that software relies on for deterministic response.

Metric: interrupt latency tail, missed-interrupt incidents