cs3330-chap5-memory-1

cs3330-chap5-memory-1 - 1 CS/ECE 3330 CS/ECE 3330 Computer...

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Unformatted text preview: 1 CS/ECE 3330 CS/ECE 3330 Computer Architecture Chapter 5 Memory ¡ Static RAM (SRAM) ¢ 0.5ns – 2.5ns, $2000 – $5000 per GB ¡ Dynamic RAM (DRAM) Memory Technology ¢ 50ns – 70ns, $20 – $75 per GB ¡ Magnetic disk ¢ 5ms – 20ms, $0.20 – $2 per GB ¡ Ideal memory ¢ Access time of SRAM CS/ECE 3330 – Fall 2009 ¢ Capacity and cost/GB of disk 1 2 ¡ Programs access a small proportion of their address space at any time ¡ Temporal locality Principle of Locality ¢ Items accessed recently are likely to be accessed again soon ¢ e.g., instructions in a loop, induction variables ¡ Spatial locality ¢ Items near those accessed recently are likely to be accessed soon CS/ECE 3330 – Fall 2009 be accessed soon ¢ E.g., sequential instruction access, array data 2 ¡ Memory hierarchy ¡ Store everything on disk ¡ Copy recently accessed (and nearby) items Taking Advantage of Locality ¡ Copy recently accessed (and nearby) items from disk to smaller DRAM memory ¢ Main memory ¡ Copy more recently accessed (and nearby) items from DRAM to smaller SRAM memory ¢ Cache memory attached to CPU CS/ECE 3330 – Fall 2009 3 3 Memory Hierarchy Levels Block (aka line): unit of copying • May be multiple words If accessed data is present in upper level • Hit: access satisfied by upper level – Hit ratio: hits/accesses If accessed data is absent • Miss: block copied from lower level...
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cs3330-chap5-memory-1 - 1 CS/ECE 3330 CS/ECE 3330 Computer...

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