Active vs Passive Agent Modes: Worked Example

Worked example

Worked Example for Active vs Passive Agent Modes focuses on stimulus/check independence score and dual-mode regression pass rate. The purpose is to turn memory observations into mechanism-backed actions with explicit owners and release-safe validation.

A field regression flags stimulus/check independence score and dual-mode regression pass rate. Proper triage locks environment tags, compares baseline vs failing traces, isolates first repeated loss transition, and validates one bounded mitigation before release.

This pattern prevents reactive tuning. The goal is to preserve both performance and reliability while avoiding hidden regressions that appear only at corner conditions.

System view

CONTROLLER QUEUE VIEW - Active vs Passive Agent Modes

read queue : [R12 bank0 row88] [R13 bank2 row88] [R14 bank0 row12]
write queue: [W44 bank3 row90] [W45 bank3 row90]

scheduler tick:
1) prioritize ready row hits
2) cap write-drain burst
3) age outstanding reads

issue stream:
cycle 40 -> RD bank0 row88 (hit)
cycle 41 -> RD bank2 row88 (parallel bank group)
cycle 42 -> ACT bank0 row12 (miss prepare)

VIP agent and checker flow (Active Passive Agents)

VIP FLOW - Active Passive Agents

testcase -> sequencer -> driver -> DUT interface
              |                    |
              v                    v
           monitor <-------- bus activity
              |
              v
        checker / scoreboard -> compliance evidence

1. Capture baseline and failing command traces under fixed metadata.

2. Verify checker hit/miss mix, turnaround cadence, and refresh impact.

3. Collect agent mode matrix, contention log, and dual-mode regression report.

4. Patch one bounded fix with explicit owner signoff.

5. Re-run closure matrix and choose ship/rollback.

VIP deep dive

Reusable VIP layering, agent roles, monitor/scoreboard contracts, and packaging patterns that scale across protocols and projects.

Concept diagram

VIP SECTION - VIP Architecture & Packaging

testcase -> agents -> checkers -> coverage -> evidence

Metric graph

checker noise vs real violations trend

Reports and artifacts

• checker hit report

• coverage closure sheet

• compliance trace matrix

• regression health snapshot

Mini case study

A profile drift caused false checker storms until configuration hashes were locked in CI.

Debug branches

• Reproduce with locked seed and profile

• Isolate checker vs scoreboard vs DUT paths

• Map failure to spec clause and owner

Senior review question

Ask: which latency, bandwidth, and reliability evidence proves this VIP topic is closed under real traffic?

Key takeaways

• Always tie controller and PHY counter shifts to application latency and throughput outcomes.

• Lock firmware timing profile, thermal condition, and DIMM state before comparing VIP captures.

Common pitfalls

• Chasing peak bandwidth while ignoring p99 latency and fairness tails.

• Changing timing guardbands without separating SI noise from scheduling issues.

• Declaring closure without reliability gates, fault injection, and regression replay.

VIP atlas notes

Active vs Passive Agent Modes should be read as an end-to-end VIP behavior, not as a single block definition. Production compliance closure reflects interactions between agents, checkers, coverage, and customer evidence before tapeout or IP release claims.

Active agents generate protocol-correct traffic while passive agents observe and check without driving the bus. Mode selection affects who owns stimulus, how monitors attach, and whether compliance suites can run against third-party DUT environments without agent contention. VIP inefficiency is multiplicative: one weak checker enable, one hollow coverage bin, or one non-reproducible failure repeated across regressions can dominate signoff risk.