DenseChip

Interface Protocols · All levels

Protocols Interview Prep

Whiteboard frameworks and protocol debug scenarios.

Whiteboard answer shape

diagram
1. Name the protocol layer.
2. Name the transaction identity.
3. State the ordering or flow-control rule.
4. Ask for waveform + transaction log + spec clause.
5. Propose the smallest experiment.
6. State the regression suite.

Scenarios

  1. scenario-axi-ordering-trap/ — Scenario: AXI Ordering Trap

  2. scenario-ddr-bandwidth-collapse/ — Scenario: DDR Bandwidth Collapse

  3. scenario-pcie-link-degrade/ — Scenario: PCIe Link Degrade

Protocol deep dive

Protocol correctness is a layered contract enforced at every boundary.

Concept diagram

diagram
intent -> transaction -> channel -> physical

Metric graph

diagram
baseline -> experiment -> target

Metrics and artifacts to collect

  • latency

  • throughput

  • error rate

  • compliance status

Mini case study

Always anchor debug to the first bad transaction.

Debug branches

  • Name layer

  • Name ID

  • Name artifact

Senior review question

Ask: what is the first transaction that deviates, and which spec rule does it test?

Practice this lesson