Multicore & System Integration

Section goal

Coherence, interconnect, NUMA behavior, and synchronization costs that dominate scaling across cores.

How to study this section

1. Start with each topic hub to establish mechanism-first framing.

2. Use reports and debug pages to separate symptoms from root cause.

3. Practice worked examples and interview drills under fixed metadata.

4. Close with checklist and silicon impact before signoff claims.

Topics

1. cache-coherence-mesi/ - Cache Coherence (MESI)

2. mesh-ring-interconnect/ - Mesh/Ring Interconnect

3. numa-and-memory-affinity/ - NUMA and Memory Affinity

4. synchronization-overhead/ - Synchronization Overhead

Related topics

• CPU Design course hub

CPU deep dive

Scaling across cores is limited by coherence and interconnect behavior before compute saturation on many workloads.

Concept diagram

MULTICORE SYSTEM VIEW

cores + private caches <-> LLC slices <-> interconnect <-> memory controllers

Metric graph

SCALING EFFICIENCY

ideal scaling        ███████████
observed under load  ███████
after policy tuning  █████████

Reports and artifacts

• coherence traffic matrix

• NoC congestion map

• NUMA locality profile

• synchronization contention report

Mini case study

A lock-heavy service regressed at higher core counts because coherence invalidations and NoC hotspots dominated.

Debug branches

• Classify traffic as coherence, demand miss, or synchronization

• Measure hotspot links instead of aggregate NoC throughput

• Validate thread and page affinity before hardware changes

Senior review question

Ask: which CPI/latency evidence proves this topic is truly closed beyond synthetic benchmarks?