Modern processors have a clock speed in the range of GHz while the main memory (DRAM) has a read/write speed in the range of MHz, so the processor needs to halt till the memory completes its request. The halt period may seem to be very small, but when seen on a broad scale, we see that most of the processor's time is wasted in the halt cycles. Cache memory is intended to reduce the speed gap between the fast processor and slow memory. When a program needs to access data from the RAM (physicalmemory), it first checks inside the cache (SRAM). Replacement policies are methods by which the memory blocks are replaced in a filled cache. Cache replacement policies play a significant role in the memory organization of a processor and dictate how fast a processor will receive the block demanded. Various replacement policies such as RRIP, ABRRIP, AIRRIP, etc. have been designed but not been implemented, unlike LRU. LRU is predominantly used in most of the systems.
