AMBA ACE: Simplified Guide

ACE stands for AXI Coherency Extensions. It's like regular AXI4, but with extra features to keep multiple processor caches in sync.

Introduction

In modern chips (like the ones in your phone), there isn't just one "Brain" (CPU). There are 4, 8, or even 16 cores. Each core has its own private "Quick Memory" called a Cache.

If Core A changes a value in its cache, Core B needs to know about it. ACE is the "Language" they use to tell each other about these changes.

What will you learn?

  • Why Coherency? The fundamental problem of stale data.
  • MOESI Protocol: The 5 states every piece of data can be in.
  • Snoop Channels: How the interconnect checks on core caches.
  • Verification: How to find bugs in these complex systems.