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Computer Science A Level > 1.1: Characteristics of Contemporary Processors (Paper 1) (SLR1-4) > Flashcards

1.1: Characteristics of Contemporary Processors (Paper 1) (SLR1-4) Flashcards

ALU, CU, Registers and Buses (1.1.1A), FDE Cycle (1.1.1B), Performance of the GPU (1.1.1C), Pipelining (1.1.1D), Von Neumann and Harvard (1.1.1D), CISC vs RISC processors (1.1.2A), GPUs and their uses (1.1.2B), Multi-code and parallel systems (1.1.2C), Input, output and storage devices (1.1.3A), Magnetic, flash and optical storage (1.1.3B), RAM and ROM (1.1.3C), Virtual Storage (1.1.3D)

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1
Q

What does the ALU do?

A

It completes all the arithmetical and logical operations

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2
Q

What is the CU?

A

A part of the processor which directs operations inside the CPU

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3
Q

What are registers?

A

Small memory cells that operate at high speeds

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4
Q

Where do all the arithmetic, logic, or shift operations occur?

A

In registers

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5
Q

What does the PC do?

A

The PC holds the address of the next instruction

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6
Q

In which part of the CPU do all calculations take place?

A

The ALU

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7
Q

Where are intermediate arithmetic and logic results stored?

A

In the ACC

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8
Q

What does the MAR do?

A

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

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9
Q

What does the MDR do?

A

Temporarily stores the data that has just been read from or the data needs to be written

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10
Q

What does the CIR do?

A

Holds the current instruction divided up into opcode and operand

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11
Q

What is a bus?

A

A set of parallel wires connecting two or more components together

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12
Q

What is the system bus?

A

The collection of the data bus, address bus, and control bus is called the system bus

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13
Q

What is the width of a bus?

A

The number of parallel wires it has

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14
Q

What is the data bus?

A

A bidirectional bus used to transport data and instructions between components

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15
Q

What is the control bus?

A

The bi-directional bus used to transmit control signals between internal and external components

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16
Q

What is the address bus used for?

A

Used to transmit the memory address specifying where data is to be sent from or retrieved from

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17
Q

What does adding a wire to the address bus do to the number of addressable locations?

A

It doubles the number of addressable locations

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18
Q

What does the Bus Request indicate?

A

Indicated a device is requesting access to the data bus

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19
Q

What does Bus Grant indicate?

A

Indicates the CPU has granted access to the data bus

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20
Q

What does memory write do?

A

Causes the data on the data bus to be written into the addresses location

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21
Q

What does memory read do?

A

Causes the data from the addressed location to be placed onto the data bus

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22
Q

What does the interrupt request control signal indicate?

A

Indicates that a device is requesting access to the CPU

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23
Q

What is the clock control signal used for?

A

It is used to synchronize instructions

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24
Q

What is assembly language?

A

Assembly language is a programming language where mnemonics are used to represent instructions

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25
Q

What is opcode?

A

Opcode is used to determine the type of instruction and what hardware to use to execute it

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26
Q

What is the operand?

A

The operand is the address of where the operation is performed

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27
Q

What occurs during the fetch phase?

A
  • The address from the PC is copied to the MAR
  • Instruction held at that address is copied to the MDR by the data bus, simultaneously the contents of the PC is incremented by 1
  • The value of the MDR is copied to the CIR
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28
Q

What occurs during the decode phase?

A

The contents of the CIR is split into operand and opcode

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29
Q

What occurs during the execute phase?

A

The opcode is executed on the data

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30
Q

What is the clock speed?

A

The number of clock cycles completed per second

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31
Q

What is cache memory?

A

Cache memory is the CPU’s onboard memory which can be accesses a lot faster than main memory

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32
Q

What is pipelining

A

The process of completing the fetch, decode and execute of three separates files simultaneously

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33
Q

What is Von Neumann architecture?

A

Architecture in which there is a single shared memory and shared data bus for both data and instructions

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34
Q

What is Harvard architecture?

A

Architecture in which there is two separate memory and data buses for data and instructions

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35
Q

What is contemporary processing?

A

Processing in which Von Neumann architecture is used for main memory. Cache uses Harvard architecture, divided into instructions, cache and data cache

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36
Q

What does RISC mean?

A

Reduced Instruction Set Computer

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37
Q

What does CISC mean?

A

Complex Instruction Set Computer

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38
Q

What are the properties of RISC?

A
  • Small instruction set
  • Each instruction is one line of machine code
  • Used in everyday devices
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39
Q

What are the properties of CISC?

A
  • A large instruction set
  • Instructions are built into hardware
  • Used in embedded systems and microprocessors
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40
Q

What are the benefits of RISC processors?

A

Pipelining is possible since each instruction takes one clock cycle

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41
Q

What are the benefits of CISC processors?

A
  • Compilers have to do less work
  • They require less RAM since instructions are smaller
42
Q

What is a GPU?

A

A co-processor made up of lots of independent parallel processors

43
Q

What are GPUs used for now?

A

Used for image processing and machine learning

44
Q

What are multi-core systems?

A

Systems where there are multiple cores that separate fetch-execute cycles

45
Q

What are parallel systems?

A

Systems where multiple instructions can be completed at any given time, doesn’t require multiple cores, it can use threading and pipelining instead

46
Q

Give two types of magnetic storage

A
  • Hard Disk Drive
  • Floppy Disk
  • Magnetic Tape
47
Q

Give three examples of input devices

A
  • Keyboard
  • Mouse
  • Microphone
  • Webcam
  • Touchpad
  • Barcode reader
  • Magnetic Stripe Reader
48
Q

Give an example of a device which is used for both input and output

A

Touchscreen

49
Q

What name is given to the areas on a CD’s surface which have been burned into grooves by a laser?

A

Pits

50
Q

Give three examples of output devices

A
  • Speaker
  • Monitor
  • Printer
  • Projector
51
Q

Which has the highest typical storage capacity: CD, DVD or Blu-Ray?

A

Blu-Ray

52
Q

In a HDD what is mounted at the end of the actuating arm?

A

Read/write head

53
Q

Which storage device has typical capacities in the range 500GB-5TB?

A

HDD

54
Q

Give 2 disadvantages of SSDs

A
  • High cost per GB
  • Limited lifespan
55
Q

How is information stored in flash memory?

A

Information is stored in blocks which are then combined to form pages

56
Q

Which two types of logic gates are used in flash storage?

A

NAND and NOR

57
Q

Give 3 advantages of SSDs

A

High transfer speeds
Lightweight
No moving parts

58
Q

Give 2 disadvantages of SSDs

A
  • Expensive
  • Limited read/writes
59
Q

What is ROM?

A
  • Small piece of read-only memory
  • Non volatile
  • Contains very first instructions for the computer (bootstrap)
60
Q

What is RAM?

A
  • Temporary storage of instructions and data
  • Holds information being executed by the processor
  • Volatile
  • Much faster than the hard disk
61
Q

What does the bootstrap include?

A
  • Contains a set of initial startup instructions placed in the ROM during manufacturing
62
Q

What is POST?

A
  • Power-on self-test
  • Sends signal to all connected components, wakes them up and makes the CPU aware of their existence
63
Q

Describe the process of a boot up

A
  • When a computer system first receives power, there are no instructions in the CPU
  • The OS is stored on secondary storage - Hard Drive
  • At this stage, the computer isn’t aware that the HDD exists
  • The solution to this is ROM, as it contains the bootstrap
  • POST is taking place
  • As the computer is now aware of the HDD, it can load the OS into RAM
64
Q

What is virtual storage?

A
  • The concept of storing and receiving data over the internet in the cloud instead of a local storage device
65
Q

What are the advantages of Cloud storage?

A
  • Data can be accessed at any time, from any device as long as there is internet access
  • Data can be easily shared without the need for removable media transfer
  • Easy collaboration
  • Storage considered to be ‘limitless’ from the user’s point of view
66
Q

What are the disadvantages of cloud storage?

A
  • Can become quite expensive
  • If connectivity is low, access times can be slow
  • No internet connection = no access to your files
67
Q

What can virtual storage also refer to?

A
  • The abstraction or separation of logical storage from physical storage
68
Q

What is meant by the term multitasking?

A
  • When you have more than one program open and running at the same time
  • The processor allocates a small amount of time to each process and cycles between them
69
Q

What is file management?

A
  • Data is stored in files
  • An extension to the filename tells the OS which application to load the file into
  • The OS may present a logical structure of files in folders and allow the user to rename, delete, copy and move files
70
Q

What is user management?

A
  • Allows multiple users to log into the same computer.
  • The OS will retain settings for each user such as icons, desktop, backgrounds etc.
  • Each user may have different access rights to files and programs
  • A client-server network may impose a fixed or roaming profile for a user and manage login requests to the network
71
Q

What are some UIs?

A
  • WIMP: Windows, Icons, Menus and pointers
  • Visual
  • Interactive
  • Intuitive
  • Optimised for mouse and touch gesture input
72
Q

What are the 2 methods of dividing memory into smaller sections?

A
  • Paging
  • Segmentation
73
Q

Describe paging

A
  • Pages are fixed size
  • Pages are made to fit sections of memory
  • Pages are physical divisions
  • Programs are split to fit into a given number of pages
  • Paging takes no account of how it splits the program, only that it splits it into fixed-sized pages
  • It could separate the instructions inside a looping condition so they are in different pages, but that wouldn’t be efficient
74
Q

Describe segmentation

A
  • Segments are different sizes
  • Segments are complete sections of programs
  • Segments are logical divisions
75
Q

What is Virtual memory?

A
  • Using parts of the HDD to store programs that can’t be stored in primary memory
76
Q

What is an interrupt?

A
  • While the processor does the FDE cycle other devices and applications may require the processor’s attention.
  • They need a way to signal to the processor that they require attention - this is what’s called an interrupt
77
Q

What is the ISR?

A
  • Interrupt Service Routine
  • A program with a set of instructions that need to be fetched, decoded and executed to carry out the operations of the interrupt
  • That means that the contents of the PC need to be changed to point to the address for the first instruction of the interrupt
78
Q

What happens when an interrupt is received?

A
  • The values held in the registers are copied into a data structure in memory known as the stack
  • These values are pushed onto the stack in a stack frame, effectively saving them for later retrieval
  • The interrupt can now be executed
  • Once the interrupt is complete, we pop the frame off the top of the stack.
79
Q

What does popping the frame of the stack allow us to do?

A
  • Retrieve the previous values for the original program
  • Load them back into the processor registers
  • Carry on executing the original program where we left off
80
Q

What happens when a high-priority interrupt comes along while an interrupt is being executed?

A
  • The stack system handles it by:
    • Suspending ISR A
    • Pushes register contents onto the top of the stack
    • Starts executing ISR B
    • Once ISR B has completed executing, we pop the frame off the top of the stack to retrieve the value for ISR A, load them back into the processor registers and carry on executing ISR A
81
Q

What are some examples of hardware interrupts?

A
  • Power supply failure
  • Power/reset button pressed
82
Q

What are some examples of user interrupts?

A
  • Moving the mouse
  • Keyboard presses
83
Q

What are some examples of software interrupts?

A
  • Illegal instructions encountered
  • Arithmetic overflow
  • New log on request
84
Q

What are some examples of timer interrupts?

A
  • Screen recording application
  • Data-logging program reading an input-sensor every second
85
Q

What are some examples of I/O devices interrupts?

A
  • Buffer nearly empty
  • Printer ink supply notification
  • Signal the completion of a data transfer to/from a device
86
Q

What does a scheduler do?

A
  • Manages which process to execute next
  • Manages the length of time the next process can execute for
87
Q

Explain the process of scheduling using Process A as an example

A
  • Process A is a new process
  • The number indicates the length of time before it finishes
  • It enters the ready queue
  • When the currently executing process finishes or is blocked or suspended, process A can move into a running state
  • From here it will either:
    • Finishing executing completely and leave the system
    • Get blocked as it requires an input or output commands, meaning it can’t continue until more data is received
    • Run out of time - each process is allocated a certain amount of time after which it is suspended and moved to the back of the ready queue
88
Q

What is an FCFS algorithm?

A
  • First come First Served
  • Processes are executed in the order they arrive
  • If a process takes a long time, the others behind it have to wait
89
Q

What is a SJF algorithm?

A
  • Shortest Job First
  • Picks the processes that take the shortest amount of time and runs them until they finish
  • The scheduler needs to know how long each process will take
90
Q

What is a RR algorithm?

A
  • Round Robin
  • Each process is allocated a fixed amount of time, known as a time slice or quantum
  • If the process isn’t complete by the end of its time slice, it returns to the back of the ready queue
91
Q

What is a SRT algorithm?

A
  • Shortest Remaining Time
  • Similar to SJF
  • Pre-emptive algorithm, meaning processes can be suspended if a higher priority process joins the queue
92
Q

What is a MLFQ algorithm?

A
  • Multi Level Feedback Queue
  • This algorithm builds upon these standard algorithms with the following design principles:
    • Separates processes into multiple ready queues based on their processing needs.
    • Gives preference to processes with high I/O bursts
    • I/O bound processes will sleep in a wait queue to give other processes CPU time
  • This algorithm allows for processes to be shifted between queues
  • If a process has too much CPU time, it will be moved to a lower priority queue
  • If a process is I/O bound or an interactive process, it will be moved to a higher priority queue
  • If a process is waiting too long in a low-priority queue, it will be moved to a higher priority queue
93
Q

What are the 5 types of OS?

A
  • Distributed
  • Multi-User
  • Real-Time
  • Embedded
  • Multi-tasking
94
Q

What is a multi-tasking OS?

A
  • An OS that handles many processes at the same time
95
Q

What is a multi-user OS?

A
  • An OS that allows more than one person to access a single computer at the same time
  • The computer will manage the user’s various permissions and access rights when they log on
  • Server operating system software will handle the requests of multiple people using different computers on a network at the same time
96
Q

What is a distributed OS?

A
  • An OS which can combine the processing power of multiple computers across a network for a single task
97
Q

What happens in distributed computing?

A
  • The operating system controls and coordinates system controls and coordinates the computers, presenting them to the user as if they were a single system
98
Q

What are embedded OS?

A
  • They run on dedicated hardware so they run with maximum efficiency, using low powered processor and very little memory
99
Q

What is a real-time OS?

A
  • An OS that executes processes within a known time frame
  • Plenty of redundancy is built into these systems so they can handle sudden increases in input
  • As such, processors in real-time OS rarely run at capacity
100
Q

What is the BIOS responsible for?

A
  • Responsible for loading the OS when the computer first turns on
  • It first checks that the hardware it needs is connected and working using a POST

Computer Science A Level (8 decks)

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