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Computer Science > 1.1 Processors > Flashcards

1.1 Processors Flashcards

CPU; FDE cycle; Factors affecting CPU performance; Pipeling; Von Neumann and Harvard architectures; CISC and RISC; GPUs; Multicore and parallel systems; I/O devices; RAM and ROM; Storage devices; Virtual storage

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1
Q

What does CPU stand for?

A

Central Processing Unit

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2
Q

What is the CPU?

A

Internal piece of hardware responsible for executing/processing instructions of programs

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3
Q

What does CU stand for?

A

Control Unit

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4
Q

What does the CU do?

A

Coordinates/synchronises activities of the CPU

Organises sequence in which program instructions are executed

Directs flow of data between CPU and other devices

Deals with inputs and outputs to the CPU

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5
Q

What does ALU stand for?

A

Arithmetic Logic Unit

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6
Q

What does the ALU do?

A

Arithmetic: complete arithmetic operations (+, -, *, /)

Logical: completes logical operations (==, >, <, !=)

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7
Q

What are registers?

A

Small memory locations inside the processor

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8
Q

What do registers do?

A

Store values/data temporarily to allow CPU fast access

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9
Q

What do general-purpose registers do?

A

Used to keep the results of intermediate calculations produced as part of a larger computation

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10
Q

What are dedicated registers?

A

Processor-based registers used for specific purpose

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11
Q

What are some examples of dedicated registers?

A

MAR

PC

ACC

MDR

CIR

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12
Q

What does MAR stand for?

A

Memory Address Register

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13
Q

What does the MAR do?

A

Stores the address of the memory location from which data/instructions are going to be fetched/written

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14
Q

What does PC stand for?

A

Program Counter

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15
Q

What does the PC do?

A

Stores address of the next instruction to be executed

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16
Q

What does ACC stand for?

A

Accumulator

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17
Q

What does the ACC do?

A

Holds results of calculations made by ALU

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18
Q

What does MDR stand for?

A

Memory Data Register

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19
Q

What does the MDR do?

A

Stores data being read from or being written to the RAM

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20
Q

What does CIR stand for?

A

Current Instruction Register

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21
Q

What does the CIR do?

A

Stores the instruction currently being executed

Stores data while it’s being decoded

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22
Q

What is data split into?

A

Opcode

Operand

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23
Q

What are buses?

A

Series of wires connecting the processor to the main memory and input/output devices

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24
Q

What are buses used for?

A

Transferring data between CPU and main memory

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25
Q

How many devices can send signals on a bus at one time?

A

One

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26
Q

What are the three types of buses?

A

Address

Data

Control

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27
Q

What is the address bus used for?

A

Transfers address to read data from or write data to between MAR and main memory

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28
Q

Is the address bus bidirectional or one direction?

A

One direction between CPU to RAM

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29
Q

What does the control bus do?

A

Transfers a read/write signal from CU to main memory

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30
Q

Is the control bus bidirectional or one direction?

A

Bidirectional

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31
Q

What does the data bus do?

A

Transfer data between main memory and the CPU

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32
Q

Is the data bus bidirectional or one direction?

A

Bidirectional

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33
Q

What is main memory?

A

Where programs and data are stored while waiting to be processed

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34
Q

What happens in the fetch stage of the FDE cycle?

A

The PC holds the address of the next instruction to be used

This address is copied into the MAR

The contents of the PC are incremented

The data found in the address in the MAR is copied to the MDR

The contents of the MDR are copied to the CIR

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35
Q

What happens in the decode stage of the FDE cycle?

A

The contents of the CIR are divided into the binary code for the operation to be carried out and probably the address of the data that will be used by the program

The CU then interprets the operation code so that the processor knows what to do next

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36
Q

What happens in the execute stage of the FDE cycle?

A

The address part of the instruction is copied from the CIR to the MAR

The data is used

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37
Q

What factors affect the performance of the CPU?

A

Number of cores

Size of registers

Size of RAM

Clock speed

Width of data bus

Cache

Word length/size

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38
Q

How does the number of cores affect the performance of the CPU?

A

Processor can have many processors/cores on a single chip, meaning that more than one instruction can be executed at one time

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39
Q

Why might there be delays on a core?

A

It requires a task on another core to be completed before continuing

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40
Q

What is parallel procesing?

A

Organising a task and sending the appropriate data and instructions to the appropriate core

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41
Q

How does the size of the registers affect the performance of the CPU?

A

Size determines the amount of data with which the computer can work at one time

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42
Q

How does the size of RAM affect the performance of the CPU?

A

More RAM, more programs and data can be held in memory

RAM is faster than a storage disk

If there isn’t enough memory, PC must move data between RAM and hard disk frequently, which is slow

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43
Q

What is clock speed?

A

Number of cycles per second

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44
Q

What is clock speed measured in?

A

Hertz

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45
Q

How does clock speed affect the performance of the CPU?

A

Faster the clock speed, the more instructions can be executed per second

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46
Q

What is the width of the data bus?

A

Number of parallel wires running between CPU and main memory

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47
Q

What does the width of the data bus determine?

A

How many bits can be transmitted between CPU and other devices

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48
Q

How does the width of the data bus affect the performance of the CPU?

A

Wider the bus, the more bits can be transferred at once, the fewer number of fetches needed

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49
Q

What else about the data bus affects the performance of the CPU?

A

The speed of the data transfer

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50
Q

What is cache?

A

High speed memory holding most recent data and instructions loaded by the CPU

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51
Q

Where is cache located?

A

Directly on the CPU so there’s faster access to them compared to RAM

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52
Q

How does cache affect the performance of the CPU?

A

The more cache, the fewer numbers of fetches

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53
Q

What is L1 cache?

A

Part of the circuitry of each core

Smallest and fastest

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54
Q

What is L2 cache?

A

Shared by cores

Slower and larger than L1

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55
Q

What is L3 cache?

A

Sits on or near the processor on the motherboard

Slower and larger than L2

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56
Q

What is L4 cache?

A

Placed on or near the processor

57
Q

What is word length/size?

A

Amount of data handled by processor at one time

58
Q

How does the word length/size affect the performance of the CPU?

A

Bigger the word length, the fewer fetches from main memory

59
Q

What is pipelining?

A

Data/processes arranged in a series where the OUTPUT OF ONE IS THE INPUT OF THE NEXT

60
Q

What does pipelining allow in the FDE cycle?

A

One task to be fetched, one decoded and one executed at the same time

61
Q

How does pipelining affect the CPU

A

Maximises the use and increases the throughput

62
Q

Why is the FDE cycle suitable for pipelining?

A

Consists of number of distinct stages that are repeated for every instruction

Between each stage, there are registers that can keep intermediate results and a clock signal that synchronises the flow of data (important to avoid overwriting data)

While one instruction is being fetched, one decoded and one executed

63
Q

What does pipelining avoid?

A

Keeping internal components idle

64
Q

What are the benefits of pipelining?

A

Instructions are executed at a faster rate

Improves processor performance

65
Q

What are the features of Von Neumann architecture?

A

Single CU

Single ALU

Makes use of dedicated registers

DATA AND PROGRAMS STORED IN THE SAME MEMORY

SINGLE BUS USED TO TRANSFER DATA AND INSTRUCTIONS

Has a method to connect I/O devices

66
Q

What is the problem with Von Neumann architecture?

A

Von Neumann bottleneck

67
Q

What is the Von Neumann bottleneck?

A

Can only fetch either data or instructions because there’s only one data bus

68
Q

What are the features of Harvard architecture?

A

DATA AND PROGRAMS ARE STORED IN SEPARATE MEMORIES

DATA AND INSTRUCTIONS ARE TRANSFERRED ALONG SEPARATE BUSES

69
Q

Where is Harvard architecture used?

A

Embedded systems

70
Q

What are the advantages of Harvard architecture?

A

Data and instructions can be fetched simultaneously

Faster

71
Q

What are the disadvantages of Harvard architecture?

A

Costs more to develop as a second bus and memory needed

More complex

72
Q

What architecture do modern computers use?

A

Mixture of Von Neumann and Harvard

73
Q

What is a CPU instruction set?

A

Group of commands for a CPU in machine language

74
Q

What are the two CPU instruction sets?

A

CISC

RISC

75
Q

What does CISC stand for?

A

Complex Instruction Set Computer

76
Q

Can CISC support pipelining?

A

No

77
Q

How many machine cycles are there per instruction for CISC?

A

Multiple

78
Q

How large is a CISC processor compared to a RISC?

A

Physically larger in size

79
Q

Is CISC more or less expensive than RISC?

A

More expensive as they require more silicon

80
Q

Does a CISC processor have more or less complex hardware than a RISC?

A

More complex hardware

81
Q

What tasks do better with a CISC processor?

A

More intensive tasks

82
Q

What is the energy consumption of a CISC processor?

A

Greater energy consumption than RISC

83
Q

Where is a CISC processor used?

A

Laptops and desktop computers, made by Intel or AMD

84
Q

What does RISC stand for?

A

Reduced Instruction Set Computer

85
Q

Can RISC support pipelining?

A

Yes

86
Q

How many machine cycles are there per instruction in RISC?

A

Single

87
Q

How large is a RISC processor in comparison to a CISC?

A

Smaller in size as less complex circuitry

88
Q

How expensive is a RISC processor compared to a CISC?

A

Cheaper because require less silicon needed

89
Q

Does a RISC processor need more or less complex circuitry compared to a CISC?

A

Simpler hardware

90
Q

What are the energy requirements of a RISC processor?

A

Lower energy requirements

Can go into ‘sleep mode’ when not actively processing

91
Q

Where is a RISC processor used?

A

Smartphones and tablets, based around ARM processor

92
Q

How many CPUs would a computers originally have?

A

Single CPU

93
Q

Why were co-processors introduced?

A

Because the demands on CPU became too great

94
Q

What are co-processors?

A

Additional processor that’s designed to complete a specific task

Executes tasks concurrently with main CPU

95
Q

What is the effect of having co-processors?

A

Increases the speed of the computer

96
Q

What does GPU stand for?

A

Graphical Processing Unit

97
Q

What were GPUs originally designed to do?

A

To handle graphics

98
Q

What is a GPU?

A

A processor that has thousands of small, simpler, more efficient cores that’s good at performing simple instructions on a large data set

99
Q

Is a GPU quicker than a CPU?

A

No

100
Q

Can a GPU run processes in parallel?

A

Yes

101
Q

What is a benefit of a GPU?

A

Has a highly parallel structure enabling it to perform many processes at one time

102
Q

What are some uses of a GPU?

A

Machine learning applications

Parallel process calculations

Bitcoin mining

Brute force decryption

103
Q

What does a multicore system mean?

A

Multiple cores in the computer, meaning more instructions can be executed simultaneously, speeding up computer

Each core on the CPU can perform FDE cycle independent of other cores

104
Q

Will a dual core processor double the performance of a computer?

A

No

105
Q

What do you need to have to be use a multicore systems?

A

Have software that takes advantage of multiple cores

Have an OS capable of using multiple cores

106
Q

What is parallel processing?

A

Breaking a task down into subtasks

Processes each subtask simultaneously on a separate core

107
Q

How does parallel processing affect the performance of a computer?

A

Speeds up the performance

108
Q

How do you implement parallel processing?

A

Multiple cores

Switching between instructions

109
Q

What is multithreading?

A

Executing a set of instructions concurrently

110
Q

What are the advantages of multi-threaded code/parallel processing?

A

Performance - can do multiple tasks in parallel

Responsiveness - tasks don’t necessarily have to wait for other tasks to finish before starting

Clearer code - tasks that are unrelated can be written in separate functions and run in different threads rather than needing to multiplexed into a single code path

111
Q

What are the disadvantages of multi-threaded code/parallel processing?

A

Complexity of code - writing and maintaining multi-threaded code is generally considered to be harder than single-threaded code

Bugs - rewriting to be multi-threaded may introduce bugs

Less clear code - tasks that need to split to balance the load on each core might become less elegant

112
Q

What are input devices?

A

Peripherals used to provide data and control signal to a computer system

113
Q

What are output devices?

A

Peripherals that reproduce or display data and information from a computer system

114
Q

What are storage devices?

A

Wide range of devices that provide persistent (permanent) storage for data files and applications

115
Q

What does RAM stand for?

A

Random Access Memory

116
Q

Is RAM volatile or non-volatile?

A

Volatile

117
Q

What is RAM used to store?

A

Programs and data in use by the processor, such as OS and applications software

118
Q

How large is RAM?

A

Usually quite large in comparison to cache but not as large as secondary storage

119
Q

How does RAM speed up the computer?

A

Allows fast access to data because it is solid state

120
Q

What does ROM stand for?

A

Read Only Memory

121
Q

Is ROM volatile or non-volatile?

A

Non-volatile

122
Q

What is ROM used to store?

A

Store the boot program (bootstrap), a small program to load the OS

Some BIOS may be stored here, but because it includes settings that change, not the whole BIOS

123
Q

How large is ROM?

A

Usually quite small

124
Q

What are programs stored in ROM or flash memory known as?

A

Firmware

125
Q

Where is ROM used?

A

Embedded systems (washing machines) to store a program that can’t be changed

126
Q

How does magnetic storage work?

A

Disk heads mounted on mechanical arms read and write the data

Multiple disk platters allow for tracks that are accessible from one position of the read-write heads forming a cylinder

127
Q

What are the advantages of magnetic storage?

A

High capacity

Inexpensive per MB

128
Q

What are the disadvantages of magnetic storage?

A

Slow

Least durable

Least portable

129
Q

How does optical storage work?

A

Data stored on pits and lands circulating outwards from the centre

A laser reads over the pits and lands and a high frequency signal is created

130
Q

Where is optical storage used?

A

To distribute music (cheap and portable)

Many computers don’t come with a device that can read optical storage

131
Q

What are the advantages of optical storage?

A

Cheap and portable

132
Q

What are the disadvantages of optical storage?

A

Lowest storage capacity

133
Q

How does solid state storage work?

A

Uses non-volatile flash memory to store information

134
Q

What are the advantages of solid state storage?

A

No moving parts so very durable and portable

Uses less power

More compact

Quieter to use

135
Q

What are the disadvantages of solid state storage?

A

Expensive

136
Q

What is virtual storage?

A

The pooling together of storage mediums to act like a single storage medium

137
Q

What are examples of virtual storage?

A

The Cloud

Network Attached Storage (NAS)

138
Q

What are the advantages of virtual storage?

A

Can easily expand amount of data storage

Multiple storage devices can be utilised into an appeared single storage device

Some forms can be cheaper

Can build redundancy and use for back up

Security will often be delegated to provider

139
Q

What are the disadvantages of virtual storage?

A

If devices go down, may not be able to access your data

If security is not sufficient, data may not be protected

For a cloud, good internet connection is required to access files without a drop in performance

Computer Science (8 decks)

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