Cache
Beginner
A small, fast memory that keeps copies of recently used data close to the processor so it doesn’t have to fetch it from far away again.
Novice
A small, fast memory that automatically keeps copies of recently used data. Data moves in fixed chunks called lines, often 64 bytes, and each line has a tag recording which memory address it came from. A hit (the data is there) takes a few clock cycles; a miss means fetching the line from the next, slower level.
Expert
Designed by capacity, line size, associativity (how many places a given line may sit), replacement policy, write policy, and number of banks and ports. Larger, more associative caches miss less but take longer and more energy per access, which is why the first-level cache is kept small enough to answer in one or two cycles.
Explained in Architecture (Design Flow).
See also: Memory hierarchy, AMAT (average memory access time), 3Cs (compulsory, capacity, conflict misses).