Reference Work Entry

Encyclopedia of Database Systems

pp 1707-1713

Memory Hierarchy

  • Stefan Manegold


Hierarchical memory system


A Hierarchical Memory System – or Memory Hierarchy for short – is an economical solution to provide computer programs with (virtually) unlimited fast memory, taking advantage of locality and cost-performance of memory technology. Computer storage and memory hardware – from disk drives to DRAM main memory to SRAM CPU caches – shares the limitation that as they became faster, they become more expensive (per capacity), and thus smaller. Consequently, memory hierarchies are organized into several levels, starting from huge and inexpensive but slow disk systems to DRAM main memory and SRAM CPU caches (both off and on chip) to registers in the CPU core. Each level closer to the CPU is faster but smaller than the next level one step down in the hierarchy. Memory hierarchies exploit the principle of locality, i.e., the property that computer programs do not access all their code and data uniformly, but rather focus on referencing on ...

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