A cache controller is a hardware component responsible for managing the data transfer between the CPU and the cache memory. Its primary functions include:
- Cache Coherence: Ensuring that all copies of data in different caches (and main memory) are consistent.
- Cache Access: Determining whether requested data is present in the cache (a cache hit) or not (a cache miss).
- Data Fetching: If a cache miss occurs, the controller fetches the required data from main memory and loads it into the cache.
- Replacement Policies: Deciding which block of data to evict from the cache when new data needs to be loaded (e.g., Least Recently Used - LRU, First-In First-Out - FIFO).
- Write Policies: Managing how data writes are handled, either immediately to main memory (write-through) or only when the cache block is evicted (write-back).
Designing a cache controller involves trade-offs between performance, complexity, power consumption, and cost.
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