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A-Level Computer Science > Components of a Computer > Flashcards

Components of a Computer Flashcards

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1
Q

Arithmetic Logic Unit

A

The ALU (Arithmetic and Logic Unit) completes all of the arithmetical and logical operations.

Arithmetical operations include all mathematical operations such as addition and subtraction on fixed or floating point numbers.

Logical operations include Boolean logic operations such as AND, OR, NOT, and XOR.

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2
Q

Control Unit

A

The Control Unit is the component of the processor which directs the operations of the CPU.

I has the following jobs:
- Controlling and coordinating the activities of the CPU
- Managing the flow of data between the CPU and other devices
- Accepting the next instruction
- Decoding instructions
- Storing the resulting data back in memory

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3
Q

Registers

A

Registers are small memory cells that operate at a very high speeds and are used to hold data temporarily.

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4
Q

Program Counter

A

Holds the address of the next instruction to
be executed.

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5
Q

Memory Address register (MAR)

A

Holds the address of a location that is to be
read from or written to.

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6
Q

Memory Data register (MDR)

A

Temporarily stores data that has been read or data that needs to be written.

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7
Q

Current instruction register

A

Holds the current instruction being executed, divided up into operand and opcode.

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8
Q

Accumulator

A

stores the result of calculations made by the ALU

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9
Q

Interrupt register

A

generates and detects interrupts

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10
Q

Buses

A

Buses are a set of parallel wires which connect two or more components inside the CPU.

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11
Q

Address Bus

A

This is the bus used to transmit the memory addresses specifying where data is to be sent to or retrieved from.

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12
Q

Data Bus

A

A bi-directional path for moving data and instructions between system components

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13
Q

Control Bus

A

A bi-directional bus to transmit command signals from the control unit to other parts of the processor

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14
Q

system bus

A

collective term for address, data and control bus

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15
Q

fetch decode execute cycle

A

The fetch-decode-execute cycle is the sequence of operations that are completed in order to execute an instruction.

Fetch phase:
- Address from the PC is copied to the MAR
- Instruction held at that address is copied to MDR by the data bus
- Simultaneously, the contents of the PC are increased by 1
- The value held in the MDR is copied to the CIR
Decode phase:
- The contents of CIR are split into operand and opcode
Execute phase:
- The decoded instruction is executed

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16
Q

Fetch

A
  1. The address of the next instruction is copied from the PC to the MAR
  2. The fetch signal is sent across the control bus. The contents of the MAR are transferred across the address bus.
  3. Instruction held at that address is copied to MDR by the data bus and the value held in the MDR is copied to the CIR.
  4. the PC increments by 1
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17
Q

Decode

A

The contents of the CIR are sent to the CU and divided. The operand contains the data or the address of the data upon which the operation is to be performed. The opcode specifies the type of instruction to be executed.

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18
Q

Execute

A

The appropriate instruction/ opcode is carried out on the data/ operand

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19
Q

program branch reason

A

occurs due to an if statement, function, procedure call or loop.

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20
Q

program branch result

A

the next instruction held in the PC is not carried out

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21
Q

Clock speed

A

Indicates the number of instructions the CPU can process per second.

The clock speed is determined by the ​system clock​. This is an electronic device which generates signals​, switching between 0 and 1. All processor activities begin on a clock pulse, and each CPU operation starts as the clock changes from 0 to 1. The clock speed is the time taken for one clock cycle to complete.

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22
Q

Clock speed Unit

A

Hertz (usually gigahertz)

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23
Q

Positives of increasing clock speed

A

you can carry out more instructions in a given time; improved performance

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24
Q

Negatives of increasing clock speed

A

more heat generated meaning computers must be cooled (either with heat sync/fan or water/oil cooling)

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25
Q

Cache memory

A

Special high speed memory used by a computer. Stores frequently used data and instructions.

Instructions fetched from main memory are copied to the cache, so if required again, they can be accessed quicker. As cache fills up, unused instructions are replaced.

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26
Q

Positives of increasing cache size

A

less time fetching data; improved performance

A computer with a larger cache is faster because it takes less time to retrieve information from its own memory than if it had to go back and fetch it from remote storage devices like hard drives and RAM.

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27
Q

negative of increasing cache size

A

expensive

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28
Q

Multiple cores

A

Multiple CPUs working on a single computer

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29
Q

positives of multiple cores

A

A core is an ​independent processor​ that is able to run its own fetch-execute cycle.

A computer with multiple cores can complete ​more than one​ fetch-execute cycle at any given time.

A computer with dual cores can theoretically complete tasks ​twice as fast​ as a computer with a single core.

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30
Q

negatives of multiple cores

A

However, not all programs are able to utilise multiple cores efficiently as they have not been designed to do so, so it is not always possible to make use of multiple cores

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31
Q

Von neumann architechture

A

This architecture includes the basic components of the computer and processor (single control unit​, ​ALU​, ​registers​ and ​memory units​) in which a ​shared memory ​and ​shared data bus​ is used for both data and instructions.

Von Neumann architecture is built on the stored program concept.

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32
Q

Harvard architecture

A
  • has physically separate memories for instructions and data more commonly used with embedded processors. This is useful for when memories have different characteristics i.e. instructions may be read only, while data may be read-write.
  • instructions and data are each served by their own buses

Physically separate memories also allows you to optimise the size of individual memory cells and their buses depending on your needs, i.e. the instruction memory can be designed to be larger so a larger word size can be used for instructions.

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33
Q

Parallel processing

A

Parallel processing is a method in computing of running two or more processors (CPUs) to handle separate parts of an overall task. Breaking up different parts of a task among multiple processors or cores will help reduce the amount of time to run a program as multi core CPUs are able to distribute the workload across multiple CPU cores.

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34
Q

SIMD

A

(parallel processing, single instruction multiple data) a single processor carries out an instruction on multiple data

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35
Q

MIMD

A

the MIMD (Multiple Instruction Multiple Data) computer architectures can execute several instructions on multiple data streams.

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36
Q

pipelining

A

overlapping stages in the fetch-execute cycle.

fetching the next instruction while the first instruction is being decoded

Helps to reduce parts of the processor such as the ALU from being idle.

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37
Q

distributed computing

A

A form of parallel processing system which spreads the load/problem over multiple computer systems.

A single job is split up into several tasks and each of these is run on a separate computer, coordinated by the operating system in such a way that it appears to be a single system.

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38
Q

pipelining advantages

A

improves efficiency

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39
Q

pipelining disadvantages

A

only good if you can predict subsequent instructions. If the wrong instruction is fetched for example if the program branches to a different instruction, it has to be thrown away wasting time.

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40
Q

RISC

A

reduced instruction set computing. Small Instruction set where each instruction is performed in one clock cycle.

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41
Q

CISC

A

Complex instruction set computing, large number of instruction each taking multiple machine cycles to carry out.

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42
Q

RISC advantages

A
  • Cheaper to design as smaller in size and requires less silicon.
  • Consume less power which means it does not get as hot.
  • Easy to install pipelining due to instructions being executed in order and at the same time (single machine cycle) which increases CPU performance.
  • Requires less complex hardware which leaves space for more registers and cache.
  • Fewer transistors needed means less power and cheaper
  • Only takes a single clock cycle
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43
Q

RISC Disadvantages

A
  • For a basic task more code needed (not as many instructions)
  • Because there are more lines of code, more RAM is needed to store the assembly level instructions.
  • The compiler has to do more work to translate high level code into machine code
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44
Q

GPU

A

The Graphical processing unit is a form of co-processor.

used for rendering graphics and carrying out a single instruction on multiple pieces of data

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45
Q

Co-processor

A

a processor designed for specific purposes which can carry out specialised tasks more quickly than a regular microprocessor. execute concurrently with the main CPU

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46
Q

CPU vs GPU

A

CPUs excel at doing complex instructions on small data sets whereas GPUs excel at simple manipulations to much larger data sets

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47
Q

Chip Multi Processor (CMP)

A

a single chip which contains 2 or more independent CPUs which can execute independent instructions

48
Q

opcode

A

the actual instruction/operation to be performed

49
Q

operand

A

the data the instruction applies to

50
Q

instruction set

A

a group of instructions that a computer can carry out. unique for computers.

51
Q

clock

A

a device that generates a timing signal which changes at a regular frequency.

52
Q

What determines the format of a machine code instruction

A
  • the word size

- the width of the address bus

53
Q

data bus width (bottle neck data bus)

A

same as the computers word size

54
Q

word

A

equal units of memory. each with separate memory addresses.

55
Q

What does the width of the address bus determine (bottle neck address bus)

A

the maximum possible memory addresses of the system

56
Q

Address bus average width

A

32 bits

57
Q

Clock signal

A

used to synchronise operations

58
Q

Bus request signal

A

the CPU has granted access to the address/data bus

59
Q

Memory write signal

A

causes data on the data bus to be written into the addressed location in RAM

60
Q

Memory read signal

A

causes data from the addressed location in RAM to be placed on the data bus

61
Q

Control signals

A
  • Memory read
  • memory write
  • bus request
  • clock signal
62
Q

Contemporary processor architectures

A

Modern high-performance CPU chips incorporate aspects of both Von Neumann and Harvard architectures

e.g. memory for both data and instructions but cache is divided into instruction and data and multiple parallel data buses

63
Q

uses of a GPU

A
  • Machine learning
  • Oil exploration
  • Image processing
  • Financial transactions
64
Q

need for secondary storage

A

Can retain contents when the computer’s power is turned off. This includes the Hard drive, optical media and solid state storage.

65
Q

input device

A

any device which allows you to get information from the outside world into a computer system so that it can be stored in a digital form

66
Q

Input device examples

A 
Key board
Card readers 
Microphones
Cameras
Barcode scanners
OMR/OCR
Mice
Sensors
Magnetic stripe reader
touch pads
67
Q

Output device

A

any device which is able to take data which is stored in a digital form and convert it into another format which wee can process e.g. sound, images or vibrations

68
Q

Output device examples

A 
speakers
plotters
printers
monitors
actuators
projectors
LEDs
69
Q

example of input AND output device

A

touch screen or games controllers

70
Q

storage device

A

any computer hardware used for temporary or permanent storage of data. They can be internal or external to a computer.

71
Q

internal storage examples

A

magnetic hard drive, ROM, RAM, internal solid state drive

72
Q

external storage examples

A

DVDs, CDs, Blue-ray, USB pens, SD card, Portable solid state drive, Mass storage tape, cloud storage.

73
Q

three types of secondary storage

A

magnetic, optical, solid-state

74
Q

magnetic storage examples

A

magnetic tape, floppy disks hard disk drives

75
Q

magnetic storage

A

where metal disks called platters are magnetised. a read-write head moves very close to the platter and is able to detect and modify the magnetic properties of the platter.

76
Q

magnetic storage positives

A

cheap large capacity

77
Q

magnetic storage negatives

A

slow access speed

moving parts make it vunerable

78
Q

optical storage examples

A

CDs, DVDs, Blue-ray disks

79
Q

optical storage

A

data is written to the surface of a reflective disk using pits (depressions) and lands. A laser beam passes over the surface of a land and the light beam reflected back is interpreted as binary values.

80
Q

Solid-State examples

A

USB pens and SD cards

81
Q

Solid-State Storage

A

uses flash memory so data is read and written directly to blocks and pages on the silicon micro-chips

82
Q

Optical storage advantages

A

Cheap
light weight and portable
Resilient

83
Q

Optical storage disadvantages

A

slow access speed
the surface of the disk degrades over time
scratches can corrupt data

84
Q

Solid-State storage advantages

A

Durable
No moving parts
fast access time

85
Q

Solid-state storage disadvantages

A

Expensive

limited lifespan - each section can only be written to a set number of times

86
Q

RAM acronym

A

Random Access Memory

87
Q

ROM acronym

A

read only memory

88
Q

RAM

A

fast read-write volatile memory that stores the data and programs the computer is currently using e.g. OS, Programs currently in use, data that the programs are accessing

89
Q

ROM

A

non-volatile read only memory embedded into the motherboard of a computer and used to hold important instructions the computer needs for starting up

90
Q

Virtual storage

A

(cloud storage) when data is stored over the internet on cloud storage instead of on local storage device

91
Q

virtual storage advantages

A

data can be accessed anywhere so long as you have internet access
data can be easily shared between devices without having to copy the data and transport it
the capacity is limitless

92
Q

virtual storage disadvantages

A

Expensive if you want to store large amounts of data

Access times can be slow if there is poor internet connection

93
Q

Buffer

A

a region of a physical memory storage used to temporarily store data while it is being moved from one place to another

94
Q

Uses of CISC

A

what most desktops use, Intel or AMD

95
Q

Uses of RISC

A

used in most smart phones and tablets based around an ARM processor

96
Q

Input devices for limited mobility

A
  • Foot mouse/pedal
  • Camera/eye tracker
  • Microphone
  • Puff/suck switch
97
Q

Foot Mouse

A

press key/click button with their foot to send signal.

98
Q

Camera/eye tracker

A

Move/blink to send signal

99
Q

Microphone

A

Make sound to send signal

100
Q

Puff/Suck Switch

A

blow/suck to send signal.

101
Q

types of interrupts

A
  • hardware
  • software
  • Input/output
102
Q

polling

A

The CPU checks with each device if it needs attention. Inefficient and wastes time as some devices will not want attention when called upon

103
Q

Hardware interrupt

A
  • shut down triggered by user pressing on/off button
  • memory parity error (when comparisons don’t match)
  • internal clock triggers suspending a running process
104
Q

Software interrupts

A
  • Arithmetic overflow

- Illegal instruction encountered

105
Q

Input/output interrupt

A
  • Buffer almost empty

- Signals the completions of data transfer between devices

106
Q

Timer Interrupts

A

Triggered regularly by a timer, to indicate that it is the turn of the next process to have processor time- this allows for multi tasking

107
Q

Why Do RISC processors result in increased battery life

A
  • smaller instruction set
  • fewer transistors/ less complex circuitry
  • less power required
108
Q

motion sensors

A
  • Alitmeter measures when the person ascends/descends
  • accelerometer measures the forces on a device as it moves
  • gyroscope measures if a user turns
109
Q

characteristics of CISC

A
  • Each instruction can take up more than one cycle
  • Many different instructions available
  • Many addressing modes available
  • Single register set
  • Instructions have a variable format
  • Complicated processor design
  • Integrated circuit is expensive
110
Q

characteristics of RISC

A
  • An instruction performs a simple task
  • Limited number of instructions available
  • Simple processor design
  • Complex tasks can only be performed by combining more than one instruction
111
Q

Why are GPUs better at rendering graphics than CPUs

A
  • CPUs are general purpose processors whereas GPUs are designed specifically for graphics and so likely to have built in circuitry / instructions for common graphics operations.
  • GPUs are able to perform an instruction on multiple pieces of data at one time which means it can perform transformations to onscreen graphics quicker than a CPU
112
Q

advantage of RISC over CISC

A
  • programs run faster due to simpler instructions

- Cheaper

113
Q

similarities between paging and segmentation

A
  • divide up memory
  • Both use indexes
  • assigned to memory when needed
  • allow programs to run without sufficient memory (virtual memory)
114
Q

what LMC instructions change the contents of the ACC

A
  • LDA
  • INP
  • SUB
  • ADD
115
Q

Which instruction set has more addressing modes

A

CISC

116
Q

Which instruction set has more transistors?

A

CISC

117
Q

How does a GPU apply multiple instructions to multiple data simultaneously

A

it has multiple ALUs

A-Level Computer Science (15 decks)

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