《计算机英语》课件Chapter 2 System Unit.ppt

2.3 Microprocessor A microprocessor incorporates most or all of the functions of a central processing unit (CPU) on a single integrated circuit (IC). 2.3 Microprocessor The CPU has two basic components: Control unit. The control unit can be thought of as the brain of the CPU itself. It tells the rest of the computer system how to carry out a program’s instructions. Arithmetic-logic unit. The arithmetic-logic unit, usually called the ALU, performs two types of operations—arithmetic and logical. 2.3 Microprocessor Three basic characteristics differentiate microprocessors: Instruction set. Word size. Clock speed. 2.3 Microprocessor Microprocessors are classified as being either RISC (reduced instruction set computer) or CISC (complex instruction set computer). RISC. A RISC microprocessor recognizes a relatively limited number of instructions. CISC. A CISC microprocessor contains a more complex set of instructions that it responds to. 2.4 Memory Memory is a holding area for data, instructions, and information. 2.4 Memory There are two main types of memory: Volatile and Non-volatile. Volatile memory, also known as volatile storage or primary storage device, is computer memory that requires power to maintain the stored information. Non-volatile memory, NVM or non-volatile storage, is computer memory that can retain the stored information even when not powered. In modern PCs, ROM is used to store the basic bootstrapping firmware for the main processor, as well as the various firmware needed to internally control self contained devices such as graphic cards, hard disks, DVD drives, TFT screens, etc, in the system. Unlike RAM, ROM cannot be written to. It contains essential information that is required every time the computer system is turned on. CMOS chips require less power, which makes them particularly attractive for use in battery-powered devices, such as portable computers. 2.5 System Clock The system clock is a circuit that emits a continuous stream of