1 Sec (2.1) Computer Architectures

2 For temporary storage of information, the CPU contains cells, or registers, that are conceptually similar to main memory cells. These registers can be classified as either 1. General purpose register or 2. Special purpose register

3 General purpose register: Serve as temporary holding places for data being manipulated by the CPU. These register hold the inputs to the ALU and provide storage space for results produced by that unit.

4 To perform an operation on data started in main memory: 1. The input is stored in the memory under the direction of CU 2. One instruction is token of the memory by CU which decodes it 3. CU sends signals to ALU and memory 4. Data transferred from memory or data is transferred to memory (from input) then to ALU 5. ALU performs the operation and send the result to memory 6. Repeat statements from Result is transferred to output from memory under the direction of CU ALUCU Memory Inputoutput

5 The bus system : For the purpose of transferring bit patterns, a CPU and main memory are connected by a collection of wires called a Bus

6 CPU and main memory connected via a bus

7 The bus system : Bus system is responsible for carrying the address, data and control signals from one part in the computer to another There are three kinds of buses: 1. address bus 2. data bus 3. control bus

8 Address bus: Is a unidirectional in which the addresses are sent from the CPU to memory

9 Data Bus: It is a bidirectional bus. If the CPU is sending information then the operation is called "WRITE" operation and data bus is working as output. If the CPU is receiving data the operation is called "READ" and data bus is working as input.

10 Control Bus: Is a set of signals which synchronize the activities of all the elements of the computer