primary cache(L1 cache, level one cache) A small, fast {cache} memory inside or close to the {CPU} chip. For example, an {Intel 80486} has an eight-{kilobyte} on-chip cache, and most {Pentiums} have a 16-KB on-chip level one cache that consists of an 8-KB {instruction cache} and an 8-KB {data cache}. The larger, slower secondary cache is normally connected to the CPU via its external {bus}. (1997-06-25)