Explain about Cache memory?

Cache Memory

Cache memory is an intermediate form of storage between the ultra-fast registers and the RAM. The CPU uses cache memory to store instructions and data that are repeatedly required to execute programs, thereby improving the overall system speed and increasing the performance of the computer. Maintaining frequency accessed data and instructions in the cache helps in avoiding the need to access the slower DRAM repeatedly. Cache memory is widely used for memory caching. Cache memory is basically a portion of memory made of high speed static RAM (SRAM) instead of the slower and cheaper DRAM which is used for main memory. Some memory caches are in-built in the architecture of microprocessors. For example, the Intel 80486 microprocessor has an 8K memory cache, and the Pentium has a 16K cache. Such internal caches are often called level 1 (L1) caches. Modern PCs also come with external cache memory, called level 2(L2) caches, which are built into the motherboard outside the CPU. Although L2 caches are composed of SRAM, they are much larger in size than L1 caches level 3 (L3), which is not normally used, is an extra cache that has a much larger size than L1 and L2 caches, but is slower than them (but faster than RAM). Working of the Cache Memory The CPU first checks whether the data or instruction is available in the cache memory. If it is not present there, the CPU reads the data or instructions from the main memory into the processor registers and also copies it into the cache memory. When the same piece of data/instruction is needed again, the CPU reads it from the cache memory instead of the main memory.