Memory Hierarchy

Smaller and faster, (per byte) storage devices Larger, slower, and cheaper (per byte) storage devices

Memory Hierarchy There are four major storage levels Internal – Processor registers and cache Main Memory – the system RAM On-line mass storage – Secondary storage Off-line bulk storage – Tertiary and Off-line storage

CACHE Memory smaller, faster memory which stores copies of the data from main memory Independent cache : Instruction cache and data cache Instruction caches are similar to data caches but the CPU only performs read accesses to the instruction cache. Data read policy Data write policy Replacement policy - LRU

Main Memory Main Memory is at next level to cache in hierarchy Volatile Primary storage Memory bus – Address bus and data bus ROM Typical time to access data is nanoseconds ( seconds)