computer organisation and architecture

Question 1

internal components of a computer

Answer 1

processor
main memory
address bus
data bus
control bus
I/O controllers

Question 2

role of processor

Answer 2

executes machine instructions that are fetched from main memory locations.
processor selects a memory location by placing the address of the location on the address bus.
data processed by machine instructions is fetched along the data bus from main memory and the results of processing are returned in the same way

control bus is used by the processor to assert actions and to allow devices to grab the attention of the processor via the interrupt mechanism when a key is pressed

Question 3

role of main memory

Answer 3

memory that can be accessed directly by the processor

main memory consists of a contiguous block of read/write, randomly accessible storage locations where instructions or data are stored as binary sequences

Question 4

role of address bus

Answer 4

underictional and used to select a specific memory location containing a word of data or an instruction.

it carrys the address of the desired location on its bus. the address bus is also used to address I/O ports during input/output operations

Question 5

role of data bus

Answer 5

provides a bidirectional path for moving data and instructions between system components

Question 6

role of control bus

Answer 6

bidirectional bus which is used to transport control signals that manage and orchestrate the operations that take place in a computer system between components.

(includes exchanging status signals between the components and transmitting clock signals required for the coordination of instructions).

Question 7

role of I/O controllers.

Answer 7

used to buffer data being sent between the processor and the device, so the processor does not have to wait for the individual device to repond

Question 8

concept of bus

Answer 8

transfer data between components

Question 9

address bus

Answer 9

used to specify the address of a memory location to either read data from or write data to that memory location

Question 10

control bus

Answer 10

used to send control signals that manage and orchestrate the operations that take place inside a computer system

Question 11

data bus

Answer 11

used to transfer data and instructions
bidirectional

Question 12

difference between von neuman and harvad

Answer 12

Harvard - execution of instructions are faster as fetching of code and data are simultaneous

Von Neumann - instructions and data have combined memory spaces (used extensively in general purpose computing systems)

Question 13

where are harvad architecture used

Answer 13

embedded systems such DSP systems

Question 14

where are von neuman used in

Answer 14

general purpose computing systems

Question 15

concept of addressable memory.

Answer 15

memory in a computer that can be accessed by the computer’s processes and is assigned to a particular place in that computer’s processor.

Question 16

stored program concept

Answer 16

Instructions are stored in the main memory. Instructions are then fetched decoded and executed by the processor which allows the program to be moved in and out of the main memory

Question 17

role of arithmetic logic unit

Answer 17

part of the processor that processes and manipulates data.

Question 18

role of control unit

Answer 18

controls the fetch decode execute cycle and sends signals to other components of the cycle

Question 19

role of clock

Answer 19

To control the speed at which instructions are retrieved and processed in the CPU

Question 20

role of generous purpose systems

Answer 20

designed to perform many tasks (tablets, PC)

Question 21

role of program counter

Answer 21

stores memory address of the next instruction to be fetched and executed

Question 22

role of current instruction register

Answer 22

stores the instructions that is currently being executed by the processor

Question 23

role of memory address register

Answer 23

stores the memory location where data in the MBR is about to be written to or read from.

Question 24

role of memory buffer register

Answer 24

holds the data that has just been read from or is about to be written to main memory.

Question 25

role of status register

Answer 25

to store information about instructions received from machines

Question 26

fetch stage of fetch decode execute cycle

Answer 26

• Contents of Program Counter transferred to Memory Address Register
• Address bus used to transfer this address to main memory
• instruction transferred using the data bus
• Contents of addressed memory location loaded into the Memory Buffer
  Register
• Transfer content of Memory Buffer Register to the Current Instruction
  Register

Question 27

decode stage in fetch decode execute cycle

Answer 27

• instructions held in the CIR is decoded by the CU (where the instruction is split – - into opcode and operand)

Question 28

During the decode and execute stages of the fetch-execute cycle the instruction
that is being processed is stored in the CIR. Explain why the instruction could
not be processed directly from the MBR.

Answer 28

• To carry out the instruction other data may need to be fetched
• Further memory fetches would overwrite the contents of the MBR

Question 29

execute stage in fetch decode execute cycle

Answer 29

• Any data required by the instruction that isn’t present in registers is fetched
• The instruction is carried out
• Results of any calculations are stored in general purpose registers or main memory

Question 30

processor instruction set

Answer 30

group of instructions that it can carry out

Question 31

what does instructions consist of

Answer 31

an opcode and one or more operands (value, memory address or register).

Question 32

immediate addressing

Answer 32

Immediate addressing: the operand is the datum.

Question 33

direct addressing

Answer 33

the operand is the address of the datum.

Question 34

interupt

Answer 34

Allows the currently executing process to be suspended

So that a device that needs the attention of the processor can be dealt with

Question 35

why is it important to save the volatile environment while the interrupt is being serviced

Answer 35

So that the currently running process can be returned to

As the interrupt will change register values

Question 36

6 factors that affect processor performance

Answer 36

multiple cores
cache memory
clock speed
word length
address bus width
data bus width.

Question 37

effect on processor performance of multiple cores

Answer 37

parallel processing can take place, therefore the speed of execution is increased

Question 38

effect on processor performance of cache memory

Answer 38

increasing size of cache, more data and instructions can be stored there, resulting in programs running faster

Question 39

effects on processor performance of clock speed

Answer 39

increasing clock speed causes instructions to executed at a faster rate.

Question 40

effects on processor performance of word length

Answer 40

increasing word length means the processor can access a larger amount of memory through direct accessing and could also allow the processor to have a larger instruction set

Question 41

effects on processor performance of address bus width

Answer 41

increasing width increases number of addressable locations and allows more memory to be installed on the computer

Question 42

effects on processor performance of data bus width

Answer 42

increasing width increases rate of data transfer

Question 43

laser printer

Answer 43

bitmap of image built in memory from page description
charge applied to drum
laser beam directed at drum
mirror is used to direct laser beams
where laser strikes drum charge is discharged
charge applied to toner
toner sticks onto where the laser struck
paper passed over drum and toner transfers to it
positively charged transfer roller assists transfer of toner to paper
heat fuses onto paper
four drums are are required for colour printing

Question 44

RFID scanners

Answer 44

RFID scanner sends signal;
Signal induces current in RFID transponder
RFID transponder sends data by radio

RFID signals processed into a format suitable for querying the database
query used to check if there is already a record for the product in the database

Question 45

Explain why the product manufacturers or supermarket owners might prefer the individual products to be identified using barcode labels

Answer 45

Barcodes are cheaper than RFID tags
Higher cost of RFID tags would be added on to prices

Question 46

Explain why the warehouse owners might prefer the individual products to be identified using RFID tags

Answer 46

the RFID tags could be read without removing products from their pallet;
RFID tags can be read from a distance (than barcodes)

Question 47

Describe the principles of operation of an optical disk drive that is used to read data
from an optical disk such as a CD-ROM or DVD-ROM

Answer 47

light is shone at disk
light is reflected back from disk which is measured
Disc spins at constant linear velocity

Data is stored on one/spiral track
Continuation of land reflects light whereas transition between land and pit scatters light
Transition between land and pit indicates a 1 and continuation of land represents 0