Structure and functions

Read the following words and word combinations and use them for understanding and translation of the text:

CPU (Central Processing Unit) – ЦПУ (центральный про-цессор)

bus - шина

to be referred to as - упоминаться как, называться

control unit - блок управления

arithmetic logic unit (ALU) - арифметическое логическое устройство (АЛУ)

register - регистр. счетчик

binary - двоичный

to be in charge of - быть ответственным за

fetch-execute cycle - цикл выполнения команды

instruction register (IR) - регистр команд

program counter (PC) - счетчик команд

main memory - оперативная память

to accomplish - выполнять

volatile - энергозависимый

cache memory - кэш-память

bus controller - контроллер шины

motherboard - материнская плата

One of the major characteristics of the von Neumann architecture is that the units that process information are separate from the units that store information. This characteristic leads to the following components of the computer:

- Central processing unit (CPU): Controls the operation of the computer and performs its data processing functions; often simply referred to as processor.

- Main memory: Stores data.

- I/O: Moves data between the computer and its external environment

- System interconnection: The mechanism that provides for communication among CPU, main memory, and I/O. A common example of interconnection is by means of a system bus, consisting of a number of conducting wires to which all the other components attach.

These components are interconnected in some fashion to achieve the basic function of the computer, which is to execute programs.There may be one or more of each aforementioned components. Traditionally, there has been just a single processor. In recent years, there has been increasing use of multiple processors in a single computer.

CPU

The most complex component is the CPU, with its major structural components being as follows:

- Control unit, which controls the operation of the CPU and hence the computer

- Arithmetic and logic unit (ALU), which performs the computer’s data processing functions

- Registers, which provide storage internal to the CPU

- CPU interconnection: the mechanism that provides for communication among the control unit, ALU, and registers.

The ALU is that part of the computer that actually performs arithmetic and logical operations on data. All of the other elements of the computer system - control unit, registers, memory, I/O - are there mainly to bring data into the ALU for it to process and then to take the results back out. In a sense, the ALU is the core or essence of a computer.

An ALU and, indeed, all electronic components in the computer are based on the use of simple digital logic devices that can store binary digits and perform simple Boolean logic operations.

Most modern ALUs have a small amount of special storage units called registers. Registers are used to store intermediate values or special data, i.e. information that is needed again immediately. Access to registers is much faster than access to memory locations.

The control unit is the organizing force in the computer, for it is in charge of the fetch- execute cycle. The steps in the processing cycle are:

- Fetch the next instruction.

- Decode the instruction.

- Get data if needed.

- Execute the instruction.

There are two registers in the control unit. The instruction register (IR) contains the instruction that is being executed, and the program counter (PC) contains the address of the next instruction to be executed.

There are several approaches to the implementation of the control unit; one common approach is a microprogrammed implementation. In essence, a microprogrammed control unit operates by executing microinstructions that define the functionality of the control unit.