What is cache memory?

Cache memory is random access memory (RAM) that a computer microprocessor can access more quickly than it can access regular RAM (Main memory). As the microprocessor processes data, it looks first in the cache memory and if it finds the data there (from a previous reading of data), it does not have to do the more time-consuming reading of data from larger memory.


Cache memory is sometimes described in levels of closeness and accessibility to the microprocessor. An L1 cache is on the same chip as the microprocessor. (For example, the PowerPC 601 processor has a 32 kilobyte level-1 cache built into its chip.) L2 is usually a separate static RAM (SRAM) chip. The main RAM (Main memory) is usually a dynamic RAM (DRAM) chip.
Cache main memory structure









Figure: Data mapping between cache and main memory



Tag Data block ( k words)










Figure: Cache arrangement


0 Word
1
2
3





2n-1

Figure: Main memory arrangement