Unit 3 Hardware

Question 1

what is the responsibility of a CPU (central processing unit) (AKA microprocessor or processor)

Answer 1

execution or processing of all the instructions and data in a computer application

Question 2

what does a CPU consist of

Answer 2

control unit (CU)
arithmetic and logic unit (ALU)
registers and buses

Question 3

what is the function of ALU

Answer 3

allows the required arithmetic or logic operations to be carried out while a program is running

Question 4

what is the function of CU

Answer 4

reads an instruction from the memory

Question 5

what is the function of the system clock

Answer 5

produce timing signals on the control bus to ensure synchronization takes place, or else the system will crash

Question 6

What is the function of RAM

Answer 6

often referred to as the immedi access store, RAM temporarily stores read/ write operations which are being carried out

Question 7

what are the 5 special purpose registers

Answer 7

Current instruction register
accumulator
memory address register
memory data/ buffer register
program counter

Question 8

function of current instruction register (CIR)

Answer 8

stores the current instruction being decoded and executed

Question 9

function of accumulator (ACC)

Answer 9

used when carrying out ALU calculations; it stores data temporarily during the calculations

Question 10

what is the function of the memory address register (MAR)

Answer 10

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

Question 11

what is the function of memory data/ buffer register (MDR)

Answer 11

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

Question 12

what is the function of the program counter (PC)

Answer 12

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

Question 13

what is the purpose of a system bus

Answer 13

connect the system to the memory and to input/ output devices

Question 14

what are the 3 system buses

Answer 14

Address bus
Control Bus
Data bus

Question 15

why are read/ write operations carried out using the RAM

Answer 15

the RAM carries out read/ write operations faster than a backing store (i.e- hard disk drive)

Question 16

what is a computer memory made up of and what do they contain

Answer 16

a computer memory is made up of a number of partitions. Each partition consists of an address and its contents

Question 17

what is the function of the address and contents within a computer memory

Answer 17

The address will uniquely identify every location in the memory and the contents will be the binary value stored in each location.

Question 18

what is the general purpose of input devices

Answer 18

input devices are main method of entering data into computer systems, they convert external data into a form the computer can understand and can then process

Question 19

what is the general purpose of output devices

Answer 19

output devices are the main method of getting data out of computer systems, Output devices show the results of computer processing in a human understandable form

Question 20

what is the function of address bus

Answer 20

carries addressees throughout the computer system

Question 21

why is an address bus unidirectional, and what is unidirectional?

Answer 21

unidirectional refers to bits being able to travel through one direction only, an address bus is unidirectional to prevent addresses being carried back to the CPU, which would be an undesirable feature

Question 22

why is the width of a bus important, for which of the system buses does the width of a bus matter

Answer 22

the width of the bus is a very important factor for address buses and data buses as this determines the amount of bits which can simultaneously be addressed at any given time.
However, since a control bus only carries signals from the control unit, there is no real need for it to be wider

Question 23

what direction can bits in the data bus travel in, and what can be contained inside a data bus?

Answer 23

The data bus is bidirectional (allowing data to be sent in both directions along the bus). This means data can be carried from CPU to memory (and vice versa) and to and from input/output devices. It is important to point out that data can be an address, an instruction or a numerical value

Question 24

what is the function of a control bus

Answer 24

It carries signals from the control unit (CU) to all the other computer components

Question 25

how is the fetch-decode-execute cycle carried out in the von neumann computer model?

Answer 25

first, the CPU checks checks for instructions, when an instruction is found, Program Counter (PC) contains the address of the memory location of the next instruction which has to be fetched. After which, This address is then copied from the PC to the memory address register (MAR); this is done using the address bus. Next, The contents (instruction) at the memory location (address) contained in MAR are then copied temporarily into the memory data register (MDR), The contents (instruction) of the MDR are then copied and placed into the Current Instruction Register (CIR), then The value in the PC is then incremented by 1 so that it now points to the next instruction which has to be fetched and lastly The instruction is finally decoded and then executed by sending out signals (via the control bus) to the various components of the computer system