计算机硬件英语(二)

计算机硬件英语
A Closer Look at the Processor and Primary Storage
美联英语提供
A program instruction or a piece of data is stored in a specific primary storage location called an address. Addresses permit program instructions and data to be located, accessed, and processed. The content of each address is constantly changing as different programs are executed and new data are processed.
程序指令和数据是存储在主存中一个特殊的位置，称为地址空间。

通过地址空间可以实现计算机对程序指令和数据的定位、访问和处理。

地址空间的内容是经常变化的，这是由于计算机一直在执行不同的程序和数据。

Another name for primary storage is random-access memory, or RAM. A special type of primary storage, called read-only memory (ROM), cannot be altered by the programmer. The contents of ROM are “hard-wired” (designed into the logic of the memory chip) by t he manufacturer and can be “read only”. When you turn on a microcomputer system, a program in ROM automatically readies the computer system for use. Then the ROM program produces the initial display screen prompt.
主存储器也称为随机存取存储器，或RAM。

还有一种特殊的主存储器，称为只读存储器（ROM），这种存储器不能被程序更改存放的内容。

ROM的内容是被生产商通过硬件电路写入的，并且不能被重写。

当你启动计算机，ROM中的一个程序会自动就绪等待计算机系统的调用，然后在显示器中显示开机提示。

A variation of ROM is programmable read-only memory (PROM). PROM is ROM into which you, the user, can load “read-on ly” programs and data. Once a program is loaded to PROM, it is seldom, if ever, changed [4]. However, if you need to be able to revise the contents of PROM, there is EPROM, erasable PROM. Before a write operation, all the storage cells must be erased to the same initial state.
可编程只读存储器（PROM）是另一种ROM，它可以载入只读的程序和数据，一旦载入，将不再改变。

然而，若果你需要去修正PROM的内容，可以使用可擦可编程只读存储器。

EPROM在进行一次写操作之前，所有的存储单元必须被还原为同一初始状态。

A more attractive form of read-mostly memory is electrically erasable programmable read-only memory (EEPROM). It can be written into at any time without erasing prior contents; only the byte or bytes addressed are updated.
一种更吸引人的可改写只读存储器是电可擦除可编程只读存储器(EEPROM)。

它可以在任何时候写入，而且不会擦除以前的内容；只会更新被寻址的字节。

The EEPROM combines the advantage of nonvolatility with the flexibility of being updatable in place [6], using ordinary bus control, address, and data lines.
电可擦可编程存储器把非易失性优点和可更新、需要更新的地方的灵活性结合起来，修改时使用普通的总线控制线、地址线和数据线。

Another form of semiconductor memory is flash memory (so named because of the speed). Flash memory is intermediate between EPROM and EEPROM in both cost and functionality. Like EEPROM, flash memory uses an electrical erasing technology. An entire flash memory can be erased in one or a few seconds, which is much faster than EPROM. In addition, it is possible to erase just blocks of memory rather than an entire chip. However, flash memory does not provide byte-level erasure [7]. Like EPROM, flash memory uses only one transistor per bit, and so achieves the high density of EPROM.
另一种半导体记忆体是闪存（意味着速度快）。

闪存在性价比上处于EPROM和EEPROM之间，它使用电擦写技术。

整个闪存的内容可以在一到几秒内被清除，这是远快于EPROM的。

另外，它还可以对部分记忆块而不是整个存储器进行清除。

然而，闪存并不提供字节级的擦除。

像EPROM，闪存只使用一个晶体管每比特，因此可以实现高密度的EPROM。

Cache Memory
Program and data are loaded to RAM from secondary storage because the time required to access a program instruction or piece of data from RAM is significantly less than from secondary storage. Thousands of instructions or pieces of data can be accessed from RAM in the time it would take to access a single piece of data from disk storage [8]. RAM is essentially a high-speed holding area for data and programs. In fact, nothing really happens in a computer system until the program instructions and data are moved to the processor. This transfer of instructions and data to the processor can be time-consuming, even at microsecond speeds. To facilitate an even faster transfer of instructions and data to the processor, most computers are designed with cache memory. Cache memory is employed by computer designers to increase the computer system throughput (the rate at which work is performed).
程序和数据从辅助存储器装载到RAM中是因为对RAM中的程序指令和数据的访问时间要明显的少于从辅助存储器访问。

数以千条的指令和数据能被访问而只需花费从硬盘访问一次数据的时间。

RAM是数据和程序的重要的高速存放区，事实上，计算机系统不会进行任何操作直到程序指令被传入处理器进行执行，这种指令和数据的传输是需要花费时间的，即使传输速度已经是以纳秒来计算了。

为了能更快速的传输指令和数据，大多数计算机设计使用高速缓存。

计算机设计者使用高速缓存来提高计算机系统的总处理能力（工作效率）。

美联英语：。