Cpu organisation
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The CPU acts as the computer's brain and carries out instructions from programs. It has two main components: the control unit, which selects and coordinates instruction execution, and the arithmetic logic unit, which performs calculations. Registers temporarily store data during instruction processing, including special purpose registers like the program counter, accumulator, and input/output registers. The CPU communicates with main memory, usually RAM, and cache memory for faster access to active data. It fetches instructions from memory and decodes and executes them in a multi-step process controlled by the control unit.
Cpu organisation
- 2. CPU (CPU (Central Processing UnitCentral Processing Unit)) Acts as the brain of computer. Performs all the calculations & controls all the components. Carries out the instructions of a computer program, performs the basic arithmetical, logical, and input and output operations of the system.
- 4. CPU Has Two MainCPU Has Two Main ComponentsComponents Control Unit (CU) Arithmetic & Logic Unit (ALU)
- 5. Control UnitControl Unit Selects program instructions & coordinates their execution. Regulates timing of processor. Sends control signal to and receives control signal from peripheral devices. Acts as central nervous system for all other components. It obtains instruction from memory, interprets the instruction & issues signals to the required units to carry out the execution.
- 6. ALUALU Actual execution of instruction takes place in ALU. It consists of a complicated set of logic circuit, registers and accumulator to carry out all operations. Depends on the commands given by the Control Unit.
- 7. RegistersRegisters It holds data temporarily during the execution of instruction. They are a part of CPU. Length of register = No. of bits in can store. Two types - Special Purpose Registers General Purpose Registers
- 8. List of Special Purpose RegistersList of Special Purpose Registers Decoder Program Control Register Memory Address Register Memory Buffer Register Instruction Register I/O Register Accumulator
- 9. Decoder It interprets the instruction to be executed. Program Control Register • It holds the address of next instruction to be executed. • In case of branch instruction, system passes the address part of branch instruction to PC. Memory Address Register It holds the address of the active memory location.
- 10. Memory Buffer Register It holds the content of accessed memory word. It holds the data word when it is transferred to and from the main memory. Instruction Register It holds the instruction being executed. Instruction is divided into two parts : Operation Part - Given to MAR Address part - Given to Decoder
- 11. I/O Register It is used for communication with the I/O devices. An input unit transfers all the contents to this register & then system picks up the data & vice-versa. Accumulator It holds the data under execution, intermediate results & result of operations. Result Accumulator MBR Main Memory
- 12. Main MemoryMain Memory RAM (Random Access Memory) Volatile Memory Every file or application opened is placed in RAM Uses Random Access Technique, i.e., the data can be directly jumped to the middle if necessary without having to read the data sequentially.
- 14. ROM (Read Only Memory)ROM (Read Only Memory) Non-volat ile Memory The inst ruct ions are st or ed by manuf act ur ers Special programs are st ored called mi cro-programs which deal wit h low-level machine f unct ions. Types of ROM --
- 15. Cache MemoryCache Memory Ext remely f ast & small memory Placed bet ween CPU & Main memor y Used f or t emporarily st or ing act ive dat a & f or minimizing t he dat a f et ch t imeCPU Cache Memory Main Memory
- 16. Steps of Execution Of InstructionSteps of Execution Of Instruction 1 ) The CUtake s addre ss o f the ne xt instructio n fro m the PC Re g iste r & re ads the instructio n fro m co rre spo nding m e m o ry addre ss into the Instructio n Re g iste r. 2) CUthe n se nds the o pe ratio n & addre ss part to De co de r & MAR re spe ctive ly. 3) De co de r inte rpre ts the instructio n se nds co m m and sig nals to the appro priate units to carry o ut the task spe cifie d. 4) As the syste m e xe cute s e ach instructio n, it lo ads the addre ss o f ne xt instructio n in PC Re g iste r & re pe ats ste ps 1 to 4.