计算机体系结构PPT教学课件-第五章 存储器结构.ppt

王奕 Estelle.ywang@gmail. com Computer Architecture 5.1 Introduction ARE THERE ANY PROBLEM IN THE MEMORY Processor-Memory Performance Gap Who Cares About the Memory Hierarchy? CPU-DRAM Gap 1980: no cache in μproc; 1995 2-level cache on chip(1989 first Intel μproc with a cache on chip) Generations of Microprocessors 及CPU与cache速度的差异 Time of a full cache miss in instructions executed: 1st Alpha: 340 ns/5.0 ns = ?68 clks x 2 or 136 2nd Alpha: 266 ns/3.3 ns = ?80 clks x 4 or 320 3rd Alpha: 180 ns/1.7 ns =108 clks x 6 or 648 Alpha 21264 is a microprocessor designed for desktops and servers. Enhance speed of memory加快存储体的速度 Component character of hardware: (小的硬件速度快但更贵，大的硬件速度慢但更便宜) Smaller hardware is faster and more expensive Bigger memories are lower and cheaper The method enhance speed of memory加快存储器速度的方法 The method (方法就是采用层次结构) Hierarchies bases on memories of different speeds and size The more closely CPU the level is,the faster the one is. The more closely CPU the level is,the smaller the one is. The more closely CPU the level is,the more expensive. Memory Hierarchy of a Modern Computer System-现代计算机存储系统层次结构 By taking advantage of the principle of locality: . Present the user with as much memory as is available in the cheapest technology. . Provide access at the speed offered by the fastest technology. What is a cache? Small, fast storage used to improve average access time to slow memory. (小、快速的存储体，用于加速对慢速存储体的访问) In computer architecture, almost everything is a cache! Registers “a cache” on variables – software managed First-level cache a cache on second-level cache Second-level cache a cache on memory Memory a cache on disk (virtual memory) TLB a cache on page table (TLB:translation-lookaside buffer 转换旁视缓冲器) Branch-prediction a cache on prediction information? 5.2 Review of the ABCs(基本知识) of Caches 36 terms of Cache Cache full associative write allocate Virtual memory dirty bit unified cache Memory stall cycl