1、 攀枝花学院本科毕业设计（论文） 外语文翻译 攀枝花学院本科毕业设计（论文） 外文译文 院 （系）： 机电工程学院 专 业： 机械设计制造及其自动化 姓 名： 贺 兵 学 号： ZJD02078 指导教师评语： 签名： 年 月 日 攀枝花学院本科毕业设计（论文） 外语文翻译 1 外语文献翻译 原文： 3.4.1CAD HARDWARE Computers There are two major types of hardware used in a CAD system. Computer and input/output (I/O) devices. In the early days of
2、 CAD. Some commercial CAD systems used proprietary computers. Today, nearly all CAD software runs on a general-purpose computer. Depending on the complexity of the CAD package, it may require a mainframe computer, a minicomputer, or simply a microcomputer. In general, the more functionalities a CAD
3、system provides, the more powerful the computer needed. Three dimensional solid modelers require much more computing than do two-dimensional drafting systems； thus, they need more powerful computers. Systems that integrate engineering analysis or simulation packages generally are more computation-in
4、tensive. A powerful computer not only speeds up the response of a CAD system, but also can support multiple users without significant performance degradation. Several other parameters and components concerning the computer also have to be considered. CAD HARDWARE random-access memory (RAM)capacity p
5、ermanent disk-storage capacity special graphics accelerator tape backups RAM is the actual physical memory (vs. virtual memory)of a computer. A small memory capacity means slow processing due to frequent swapping between the physical memory and the virtual memory on disk. Because CAD is extremely st
6、orage demanding, disk capacity is important. Small disk capacity limits the system to the storage of only a few drawings. CAD is graphics-based and requires tremendous data processing. A graphics accelerator can drastically increase the performance of the system. Another component, the hard disk, is
7、 typically the major cost of a computer system. Therefore, it is not cost-justifiable to store all drawings on line on disk. Magnetic tape is still the most economical medium to use for off-line data storage. It is necessary for a CAD system to have a tape backup subsystem. Currently, all levels of
8、computers are used in CAD systems. Personal computers are used in low-cost,2-D drafting applications, and with the new power of these computers, hey are also being used for some 3-D solid modeling applications. Engineering workstations have been the mainstay in CAD, and are usually a single-user CAD workstation in a network. Minicomputers are used in multiuser CAD systems. Mainframes are used for large multiuser CAD systems to support real time simulation and engineering analysis. Sometimes, in a large corporation, all levels
