存储器子系统的组成与接口

存储器子系统的组成与接口(中文3600字,英文2100字)
本节我们将讨论计算机中存储器子系统的结构和功能，我们将会回顾不同类型的物理存储器及其芯片的内部组成，讨论存储器子系统的结构，以及多字节的组织和高级存储器的组成。
1 存储器的种类
存储器芯片有两种类型：只读存储器（ROM）和随机存取存储器（RAM）。只读存储器芯片是为数据（此数据可包括程序的指令）只读的应用而设计的。这些芯片在加入系统之前，就已经被某个外部编成器装好数据了。这个工作一旦完成，其数据通常不再改变。ROM芯片总是保存有数据，甚至在芯片断电以后。例如，一个微波炉的嵌入式控制器可以连续运行一个不变的数据。这就是我们在个人电脑广告上经常看到的X MB的内存所指的那种类型。不像ROM，RAM芯片一旦掉电，数据就会消失。许多计算机系统，包括个人电脑，都同时拥有ROM和RAM。

英文原文
Memory Subsystem Organization and Interfacing

In this section we examine the construction and functions of the memory subsystem of a computer. We review the different types of physical memory and the internal organization of their chips. We discuss the construction of the memory subsystem, as well as multibyte word organizations and advanced memory organizations.
1 Types of Memory
There are two types of memory chips ; read only memory(ROM) and random access memory(RAM). Read Only Memory(ROM) chips are designed for applications in which data is only read. (This data can include program instructions.)These chips are programmed with data by an external programming unit before they are added to the computer system. Once this is done, the data usually does not change. A ROM chip always retains its data, even when power to the chip is turned off. As an example, an embedded controller for a microwave oven might continuously run one program that does not change. That program would be stored in a ROM.
Random Access Memory (RAM), also called read/write memory, can be used to store data that change. This is the type of memory referred to as X MB of memory in ads for PCs. Unlike ROM,RAM chips lose their data once power is shut off. Many computer system, including personal computers, include both ROM and RAM.
2 Internal Chip Organization