muistivälimuistin

Muistivälimuisti, often referred to simply as cache, is a high-speed data storage layer that sits between a processor and main memory. Its primary purpose is to speed up data retrieval by storing frequently accessed information closer to the processor. When the processor needs data, it first checks the cache. If the data is found there (a cache hit), it can be retrieved much faster than from the main memory. If the data is not in the cache (a cache miss), the processor must fetch it from the slower main memory, and a copy of this data is typically placed in the cache for future use.

Caches are essential for modern computing performance. Processors operate at speeds far exceeding the access times of main memory (RAM). Without a cache, the processor would spend a significant amount of time waiting for data, severely limiting overall system speed. Caches are typically implemented using SRAM (Static Random-Access Memory), which is faster but more expensive and less dense than DRAM (Dynamic Random-Access Memory) used for main memory.

There are often multiple levels of cache within a processor, denoted as L1, L2, and L3. L1 cache is the smallest and fastest, located directly on the processor core. L2 cache is larger and slightly slower, also often per core, while L3 cache is the largest and slowest of the on-chip caches, typically shared among multiple cores. The hierarchical structure allows for a balance between speed, size, and cost. Managing the data within the cache, including deciding what to keep and what to evict, is handled by complex cache coherence protocols and replacement algorithms.