From The Free On-line Dictionary of Computing (30 December 2018) :
primary cache
L1 cache
level 1 cache
level one cache
(L1 cache, level one cache) A small,
fast cache memory inside or close to the CPU chip.
Intel+80486+has+an+eight-{kilobyte">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)