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Memory Hierarchy. Larger, slower, and cheaper (per byte) storage devices. Smaller and faster, ( per byte) storage devices. Memory Hierarchy. There are four major storage levels Internal – Processor registers and cache Main Memory – the system RAM
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Larger, slower, and cheaper (per byte) storage devices Smaller and faster, (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 10-100 nanoseconds (10-8 -10-7 seconds)