Computer Architecture

Transcription

1 Computer Architecture A computer system has three main components: a Central Processing Unit (CPU) or processor, a Memory Unit and Input /Output Units (devices). In any microcomputer system, the component which actually processes data is entirely contained on a single chip called Microprocessor (MPU). This MPU can be programmed using assembly language. Writing a program in assembly language requires a knowledge of the computer hardware (or Architecture) and the details of its instruction set. The main internal hardware features of a computer are the processor, memory and registers (registers are special processor components for holding address and data). The external hardware features are the computer Input/Output devices such as keyboard, monitor Software consists of the operating system (O.S) and various programs and data files stored on disk A MICROPROCESSOR is a multipurpose programmable logic device that reads binary instructions from a storage device called memory accepts binary data as input and processes data according to those instructions and provides results as input. Intel introduced its first 4-bit microprocessor 4004 in 1971 and 8-bit microprocessor 8008 in These microprocessors could not survive as general purpose microprocessors due to their design and performance limitations. Launching of the first general purpose 8-bit microprocessor 8080 in 1974 by Intel is considered to be the first major stepping stone towards the development of advanced microprocessors. ~1~

2 The microprocessor 8085 followed 8080, with a few more features added to its architecture, which resulted in a functionally complete microprocessor. The main limitations of the 8-bit microprocessors were their low speed of execution, low memory addressing capability, limited number of general purpose registers and a less powerful instruction set. All these limitations of the 8-bit microprocessors tempted the designers to go for more powerful processors in terms of advanced architecture, more processing capability, larger memory addressing capability and a more powerful instruction set. The 8086 was a result of such developmental design efforts. In the family of 16-bit microprocessors, Intel's 8086 was the first one launched in The introduction of the 16-bit processor was a result of the increasing demand for more and more powerful and high speed computational resources microprocessor has a much more powerful instruction set along with the architectural developments which imparted substantial programming flexibility and improvement in speed over the 8-bit microprocessors. The architecture of 8086 provides a number of improvements over 8085 architecture. It supports a 16-bit ALU, a set of 16-bit registers and provides segmented memory addressing capability, a rich instruction set, powerful interrupt structure, fetched instruction queue for overlapped fetching and execution etc. ~2~

3 Computer Compenants All types of computers follow a same basic logical structure and perform the following five basic operations for converting raw input data into information useful to their users. No. Operation Description 1 Take Input The process of entering data and instructions into the computer system 2 Store Data Saving data and instructions so that they are available for processing as and when required. 3 Processing Data Performing arithmetic, and logical operations on data in order to convert them into useful information. 4 Output Information 5 Control the workflow The process of producing useful information or results for the user, such as a printed report or visual display. Directs the manner and sequence in which all of the above operations are performed. ~3~

4 1. Input / Output Units This unit contains devices with the help of which we enter data into computer. This unit makes link between user and computer. The input devices translate the information into the form understandable by computer. Output unit consists of devices with the help of which we get the information from computer. This unit is a link between computer and users. Output devices translate the computer's output into the form understandable by users. 2. CPU (Central Processing Unit) CPU is considered as the brain of the computer. CPU performs all types of data processing operations. It stores data, intermediate results and instructions(program). It controls the operation of all parts of computer. CPU Operations The CPU or processor acts as the controller of all actions or services provided by the system. The operations of a CPU can be reduced to three basic steps: fetch, decode, and execute. Each step includes intermediate steps, some of which are: 1- Fetch the next instruction: - Place it in a holding area called a queue. 2- Decode the instruction - Perform address translation. - Fetch operand from memory. 3- Execute the instruction. - Perform the required calculation. - Store results in memory or register. - Set status flag attached to the CPU. ~4~

5 Start Fetch Instruction Decode Instruction CPU operations Fetch Operand Execute Instruction CPU consists of the following features: CPU is considered as the brain of the computer. CPU performs all types of data processing operations. It stores data, intermediate results and instructions(program). It controls the operation of all parts of computer. CPU itself has following two components. Control Unit ALU(Arithmetic Logic Unit) ~5~

6 Control Unit This unit controls the operations of all parts of computer but does not carry out any actual data processing operations. Functions of this unit are: It is responsible for controlling the transfer of data and instructions among other units of a computer. It manages and coordinates all the units of the computer. It obtains the instructions from the memory, interprets them, and directs the operation of the computer. It communicates with Input/output devices for transfer of data or results from storage. It does not process or store data. ALU(Arithmetic Logic Unit) This unit consists of two subsections namely Arithmetic section ~6~

7 Logic Section Arithmetic Section Function of arithmetic section is to perform arithmetic operations like addition, subtraction, multiplication and division. All complex operations are done by making repetitive use of above operations. Logic Section Function of logic section is to perform logic operations such as comparing, selecting, matching and merging of data. 3. Memory or Storage Unit This unit can store instructions, data and intermediate results. This unit supplies information to the other units of the computer when needed. It is also known as internal storage unit or main memory or primary storage or Random access memory(ram). Its size affects speed, power and capability. Primary memory and secondary memory are two types of memories in the computer. Functions of memory unit are: stores programs and data organized as» bit» byte = 8 bits (smallest addressable location)» word = 4 bytes (typically; machine dependent) instructions consist of operation codes and addresses ~7~