Cache Memory

Cache memory is a small, very fast memory placed close to the CPU that stores copies of data and instructions the processor is likely to need again soon. Reading from cache is much faster than reading from main memory (RAM), so it reduces the time the CPU spends waiting.

Modern processors have several levels: L1 cache is the smallest and fastest and sits inside each core, L2 is larger and slightly slower, and L3 is shared between cores. When the data is found in the cache it is called a cache hit; when it is not, a cache miss, and the data is fetched from RAM.