[外语学习]计算机英语第三版 1-14作者：刘兆毓、郑家农普通高等教育“十一五”国家级规划教材.ppt

* PART 1 COMPUTER HARDWARE CHAPTER 1 PRINCIPLES OF COMPUTER ORGANIZATION 1.4 MEMORY SYSTEMS chapter 1-1.4 1.4 MEMORY SYSTEMS Main point: Main point: ● Memory system specifications ● Hierarchical structure of memory ● Devices and operation of memory * RAM * Magnetic recording devices * ROM ● Magnetic disk * Cache ● Magnetic tape * CD-ROM 1.4 MEMORY SYSTEMS 1. Memory System Desiderata The memory system has three desiderata. (1) Size: infinitely large, no constraints on program or data set size. (2) Speed: infinitely fast, latency equal to the fastest memory technology available［1］. (3) Cost: the per bit cost should approach the lowestcost technology available. 1. Memory System Desiderata 2. Hierarchical Memory In this section it is shown how designers implement a Clearly these specifications cannot all be achieved as they are mutually exclusive. However, with the semiconductor and magnetic memory technology of today,these specifications are closely approximated. ?1 ● Point the three desiderata of memory system and give their technical specification separately *?1 原因状语 从句 2. Hierarchical Memory In this section it is shown how designers implement a practical memory that approaches the performance of an ideal memory at reasonable cost. This memory system has a hierarchy of levels: The memory closest to the processor is fast and relatively small, but has a high cost per bit. This level is called the cache; The real memory, sometimes known as main memory, is slower, larger, and has a lower cost per bit than the cache; 2. Hierarchical Memory 宾语从句 定语 从句 The lowest level in the hierarchy is usually a magnetic disk that has the longest latency and the lowest bandwidth; however, it can be very large and has a very low cost per bit. This