CENTRAL PROCESSING UNIT CPU (microprocessor) The central processing unit (CPU) performs operations on data. Fetches instructions from main memory. stores data, intermediates results and program. It controls the operation of all parts of computer Carries out the operations commanded by the instructions(program) Each instruction produces some outcome A program is an entire sequence of instructions Instructions are stored as binary numbers Binary number - a sequence of 1’s and 0’s

Identify the CPU on the motherboard

Identify the CPU on the motherboard

EXAMPLES OF MICROPROCESSOR PENTIUM 4 PENTIUM R PENTIUM 3 MAC PENTIUM 2 Cyrix CELRON DUAL CORE

CPU COMPONENTS In most architectures it has three parts: an arithmetic logic unit (ALU), a control unit and a set of registers, fast storage locations.

CPU COMPONENTS: ALU Control Unit A set of registers

Central Processing Unit Output Devices Cache Memory Primary Storage Secondary Control Unit ALU Special Purpose Processors Input

Mathematics Department ALU The actual processing of the data and instruction are performed by Arithmetic logic Unit It Accepts and process data The major operations performed by the ALU are addition, subtraction, multiplication, division, logic and comparison. Data is transferred to ALU from storage unit when required Mathematics Department

ALU Arithmetic operations: Logical operations:NOT ;AND;OR; XOR Increment Decrement Add Subtract Multiply Divide Logical operations:NOT ;AND;OR; XOR Comparing Selecting Merging Matching of data

Control Unit Like the part of the human brain that control the operation of each part of the body. Controlling is achieved through wires (form Control unit to ALU) that can be on/off. 4 wires  16 operations

Mathematics Department Control Unit (CU) The Control Unit acts like the supervisor i.e controls It extracts instructions from memory and decodes and executes them, and sends the necessary signals to the ALU to perform the operation needed. The control unit determines the sequence in which computer programs and instructions are executed. Process programs stored in the main memory. interpret the instructions and issue signals for other units of the computer to execute them. Mathematics Department

Register A special, high-speed ,stand-alone ,temporary storage area within the CPU. All data must be represented in a register before it can be processed. For example, if two numbers are to be multiplied, both numbers must be in registers, and the result is also placed in a register. The power and speed of a CPU determined by the number of registers that a CPU has and the size of each (number of bits) For example a 32-bit CPU is one in which each register is 32 bits wide. Therefore, each CPU instruction can manipulate 32 bits of data.

Mathematics Department Registers: The CPU processes data and instructions with high speed, there is also movement of data between various units of computer. It is necessary to transfer the processed data with high speed and remember the various addresses of data for effective functioning of CPU. So the computer uses a number of special memory(working space/temporary storage) units called registers. They are not part of the main memory but they store data or information temporarily and pass it on as directed by the control unit. Mathematics Department

Register Organization • Total of 37 32-bit registers — 31 are referred to as general purpose register although some such R15 (PC) have special purposes — Six program status registers • Registers are arranged in partially overlapping Program status registers Current Program Status Register General Purpose Registers Program Status Register User Visible Registers Control and Status Registers

Registers Types of PC (Program Counter) Current Instruction Register Keep track of the instruction currently being executed. Incremented after execution of the instruction. Current Instruction Register Store the instruction currently being executed Data Registers Hold data before it can be processed

Functions of CPU Register Temporarily store data required for processing Stores addresses of data being executed Determines the power and speed of CPU- i.e its determinant is the number and size of cpu registers Pass data onto other parts of computer as directed by the control unit. it helps transfer data and instructions with high speed Hold data before it can be processed Store the instruction currently being executed Keep track of the instruction currently being executed Incremente after execution of the instruction

Measurements of Computer Power Clock speed: electronic pulses used to synchronize processing. Faster clock speeds result in more operations in a give amount of time. Measured in megahertz (MHz). Bus width: determines how much data can be transferred at any one time. 16 bit, 32 bit, 64 bit. IBM’s Microchannel (MCA) Architecture vs EISA (open architecture) Word size: number of bits/bytes manipulated at once. Same as the bus width. Other determinants include main memory capacity, MIPs. This is not the same as throughput but it can affect throughput.. 18