DRAM Whiteboard Framework

Whiteboard flow

1. Draw request -> controller -> command bus -> bank/row -> PHY path.
2. Mark metric target and failure observation.
3. Highlight first failing transition and why it repeats.
4. Name proving artifact and accountable owner.
5. Show minimal fix and rollback trigger.

Key takeaways

• Strong answers tie command behavior to product-level impact.

• Never skip owner accountability and regression gates.

DRAM deep dive

DRAM closure requires timing-aware evidence, reproducible traffic captures, and explicit owner accountability.

Concept diagram

request stream -> controller policy -> DRAM timing behavior -> measured outcome

Metric graph

latency/bandwidth trend

Reports and artifacts

• latency breakdown report

• bandwidth efficiency sheet

• reliability gate dashboard

Mini case study

Pin firmware timing profile and thermal state before comparing DRAM traces.

Debug branches

• Reproduce and isolate before retuning timing

Senior review question

Ask: which latency, bandwidth, and reliability evidence proves this DRAM 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 DRAM 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.