INTRODUCTION TO CPUThe central processing unit (CPU) is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input and output operations of the system. It acts as the BRAIN OF COMPUTER.
HI S TORY OF CPUEarly CPUs were custom-designed as a part of a larger, sometimes one-of-a-kind, computer. However, this method of designing custom CPUs for a particular application has largely given way to the development of mass-produced processors that are made for This standardization began in the era of discrete transistor mainframes and minicomputers and has rapidly accelerated with the popularization of the integrated circuits (IC).
The IC has allowed increasingly complex CPUs to be designed and manufactured to tolerances on the order of nanometres. Both the miniaturization and standardization of CPUs have increased the presence of digital devices in modern life far beyond the limited application of dedicated computing machines. Modern microprocessors appear in everything from automobiles to cellphones and childrens toy.
BLOCK DIAGRAM OF CPU
COMPONENTS OF CPUCONTROL UNIT(CU)ARITHEMATIC LOGIC UNIT (AU)A number of Registers
CONTROL UNIT (CU) Control Unit controls operations of other parts of CPU as well as all parts of computer by sending a control signal, e.g. control sequence of instruction to be executed control flow of data among all parts of computer interpret instructions regulate timing of procressor send control single to and recieve control single from peripheral devices
ARITHMETIC AND LOGIC UNIT (ALU) Arithmetic and Logic Unit consists of a complicated set of logic circuit and accumulator. It is mainly reponsible for : Calculation Logical comparsion and decision
REGI S TERS Register is a sepecial memory used by the CPU for temperarily storing data during execution of instruction Intruction Decoder It is a device which interprets the instruction to be executed. Programer Counter (PC) It holds the address of next instruction to be executed. Instruction Register (IR) It holds the instruction being executed. Process Status Register It holds “processor bit" about operation done by ALU.
Accumulator (ACC) It stores intermediate and final results of calulation. Its the main working area of ALU. General Purpose Register It can be used to store any temperary information during execution of instruction. Memory Address Register (MAR) It holds address the data word to be accessed. Memory Data Register (MDR) It holds the data word when it is transferred to and from the main memory. Address Decoder It interprets the address in the MAR and selects the appropriate cell in the main memory to be accessed.
How CPU works?The CPU is centrally located on themotherboard. Since the CPU carries out alarge share of the work in the computer,data pass continually through it. The datacome from the RAM and the units(keyboard, drives, etc.). After processing,the data is sent back to the RAM and theunits. The CPU continually receivesinstructions to be executed. Eachinstruction is a data processing order.
MOTHERBOARDA motherboard is the physicalarrangement in a computer thatcontains the computers basic circuitryand components. On the typicalmotherboard, the circuitry is imprintedor affixed to the surface of a firmplanar surface and usuallymanufactured in a single step. Thecomputer components included in themotherboard are: The microprocessor(Optionally) coprocessors Memory BIOSExpansion slots Interconnectingcircuitry Additional components can beadded to a motherboard through itsexpansion slots.
MICROPROCESSORA microprocessor is a computerprocessor on a microchip. Its sometimescalled a logic chip. It is the "engine" thatgoes into motion when you turn thecomputer on. A microprocessor isdesigned to perform arithmetic and logicoperations that make use of smallnumber-holding areas called registers.Typical microprocessor operations includeadding, subtracting, comparing twonumbers, and fetching numbers from onearea to another.
These operations are the result of a set ofinstructions that are part of the microprocessordesign. When the computer is turned on, themicroprocessor is designed to get the firstinstruction from the basic input/output system(BIOS) that comes with the computer as part ofits memory. After that, either the BIOS, or theoperating system that BIOS loads into computermemory, or an application program is "driving"the microprocessor, giving it instructions toperform.
IMAGES OF MICROPROCESSOR
MICROCHIPA microchip (sometimes justcalled a "chip") is a unit ofpackaged computer circuitry(usually called an integratedcircuit) that is manufactured froma material such as silicon at avery small scale. Microchips aremade for program logic (logic ormicroprocessor chips) and forcomputer memory (memory or
IMAGES OF MICROCHIP
BIOSBIOS is an integral part of the computer andcomes with it when you bring it home. (Incontrast, the operating system can either bepreinstalled by the manufacturer or vendor orinstalled by the user.) BIOS is a program thatis made accessible to the microprocessor onan eraseable programmable read-onlymemory (EPROM) chip. When you turn on thecomputer, the microprocessor passescontrol to the BIOS program, which is alwayslocated at the same place on EPROM.
When BIOS boots up (starts up) the computer, it firstdetermines whether all of the attachments are inplace and operational and then it loads the operatingsystem (or key parts of it) into the computersrandom access memory RAM from the hard disk ordiskette drive. With BIOS, the operating system andits applications are freed from having to understandexact details (such as hardware addresses) aboutthe attached input/output devices. When devicedetails change, only the BIOS program needs to bechanged. Sometimes this change can be madeduring the system setup. In any case, neither theoperating system or any applications you use needto be changed.