993-计算机组成与结构.pptVIP

ECE 313 Fall 2006 Lecture 20 - Memory 计算机组成与结构 Lecture 20 – 层次结构的存储器 Reading: 7.1-7.3 Homework: 7.1-7.4, 7.9, 7.12, 7.14, 7.39 Roadmap for the term: major topics Overview / Abstractions and Technology Instruction sets Logic arithmetic Performance Processor Implementation Single-cycle implemenatation Multicycle implementation Pipelined Implementation Memory systems 3 Input/Output Outline - Memory Systems Overview 3 Motivation General Structure and Terminology(术语) Memory Technology Static RAM Dynamic RAM Disks Cache Memory Virtual Memory Memory Systems - the Big Picture Memory provides processor with Instructions Data Problem: memory is too slow and too small Memory Hierarchy - the Big Picture Problem: memory is too slow and too small Solution: memory hierarchy（层次）-分层存储器 Why Hierarchy Works The principle of locality（局部性原理） Programs access a relatively small portion of the address space at any instant of time.-在任一瞬间，程序只访问地址空间中的一小部分 Temporal locality: recently accessed data is likely to be used again Spatial locality: data near recently accessed data is likely to be used soon Result: the illusion (幻想) of large, fast memory Memory Hierarchy - Speed vs. Size Memory Hierarchy – Terminology术语 存储器层次结构的几个术语 Hit: 处理器需要的数据出现在高层的某个块中 (green block) Hit Rate: the fraction of memory accesses that “hit” Hit Time: time to access the upper level(time to determine hit/miss + access time) Miss: data must be retrieved from block in lower level (orange block) 缺失率 Miss Rate = 1 - (Hit Rate) Miss Penalty: Time to replace block in upper level + Time to deliver data to the processor Hit Time Miss Penalty and Hit Rate Miss Rate Typical Memory Hierarchy - Details Registers - Small, fastest on-chip storage Managed by compiler and run-time system Cache - Small, fast on-chip storage Associative lookup - managed by hardware Memory - Slower, Larger off-chip storage Limited size 16Gb - managed by hardware, OS Disk - Slowest, Largest off-chip storage Virtual memory – simulate a lar