Cache that is closest to the processor: typically located inside the CPU chip. Can be implemented either as a unified cache or as separate sections for instructions and data. Also referred to as Level 1 cache or internal cache.
The on-chip cache memory, closest to the execution units and with smallest latency. In the MIPS R10000 CPU, primary cache is 32KB organized in 32-byte units. Also called L1 (level-one) cache. See cache, secondary cache.