Unit 3

the Central Processing Unit processes instructions and data that are input into the computer to output the result

control unit(CU) Arithmetic and Logic Unit(ALU) registers and buses

arithmetic and logic unit does the required arithmetic or logic such as operations computers can have multiple ALU’s

a type of integrated circuit on a single microchip

control Unit reads instructions from memory The control units ensures synchronisation of data flow and program instructions through the computer

used to produce timing signals on the control bus to ensure synchronisation without it the computer would crash

current instruction register stores the current instruction being decoded and executed

accumulator stores data temporarily thats used for the calculations in the ALU

memory address register stores the address of the memory location currently being read from or written to

memory data register stores data which has just been read from memory is about to be written to memory

program counter stores the address where the next instruction to be read can be found

used in computers as parallel transmission components address bus, data bus, control bus

carries addresses throughout the computer system it is unidirectional(one direction)

bidirectional used to carry data from CPU to memory and vice versa also to and from input and output devices

bidirectional carries signals from the control unit to all other computer components

• the PC contains the address of the memory location of the next instruction • address is then copied from the PC to the MAR through the address bus • the data at the location are then copied temporarily into the MDR • the contents of the MDR are then copied and placed into the CIR • value in PC is incremented by 1 so it points to the next instruction which has to be found • instruction is decoded and executed by sending out signals through the control bus to the various components of the computer system

increasing the width allows more data to flow meaning the CPU works faster

if the clock speed becomes higher than the computer was designed for can cause the computer to be unsynchronised and cause the computer to crash can lead to overheating and unreliable performance

can also improve CPU performance located inside the CPU meaning faster access times stores frequently accessed instructions and datas larger the cache size the better the CPU performance

using more cores can improve computer performance however increasing the number of cores means the the CPU needs to communicate more with each core so potential performance is reduced

a list of all commands that can be processed by a CPU and the commands are machine code

combination of hardware and software which is designed to carry out a specific set of functions

they are small cheap to make consume little power can be controlled remotely reliable due to mass production

a series of dark and light parallel lines of varying thickness