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Cache is a high-speed storage mechanism. Level 2 cache (External cache) is a memory cache that is external to the CPU chip. Typically located on the motherboard, the L2 cache is also known as a "secondary cache." L2 caches sit between the CPU and the DRAM. An L2 cache feeds the L1 cache. If the L2 cache is also integrated on the CPU chip, then the external motherboard cache becomes the L3 cache. The L3 cache feeds the L2 cache, which feeds the L1 cache, which feeds the CPU.
Cache Level
The level of cache is determined referring to its connecting circuits or electronic pathways (bus) and physical proximity to the CPU.
Internal Cache (Level I or L1)
Internal cache is a small amount of SRAM placed inside the actual CPU (internally) and is accessed directly. It runs at the same speed as the processor. With the introduction of the 486 CPU, Intel placed 8K of internal cache memory in the processor. The present computers have 16K - 64K of L1 cache memory.
