From The Free On-line Dictionary of Computing (19 January 2023):
primary cache
L1 cache
level 1 cache
level one cache
<hardware, architecture> (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)