If you are referring to the L2 and L3 cache then this is what it is...
A CPU cache
is a cache
used by the central processing unit
of a computer
to reduce the average time to access memory
. The cache is a smaller, faster memory which stores copies of the data from the most frequently used main memory
locations. As long as most memory accesses are cached memory locations, the average latency
of memory accesses will be closer to the cache latency than to the latency of main memory.
When the processor needs to read from or write to a location in main memory, it first checks whether a copy of that data is in the cache. If so, the processor immediately reads from or writes to the cache, which is much faster than reading from or writing to main memory.
Most modern desktop and server CPUs have at least three independent caches: an instruction cache
to speed up executable instruction fetch, a data cache
to speed up data fetch and store, and a translation lookaside buffer
used to speed up virtual-to-physical address translation for both executable instructions and data.