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A-level Computer Science > 1.1 - CHARACTERISTICS OF CONTEMPORARY PROCESSORS, INPUT, OUTPUT AND STORAGE DEVICES. > Flashcards

1.1 - CHARACTERISTICS OF CONTEMPORARY PROCESSORS, INPUT, OUTPUT AND STORAGE DEVICES. Flashcards

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1
Q

What is the processor?

A

The brain of a computer. It executes instructions which allows programs
to run.

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2
Q

What is the ALU (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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3
Q

What is the CU (Control Unit) ?

A

The Control Unit is the component of the processor which directs the operations of the
CPU. It 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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4
Q

What are Registers?

A

Registers are small memory cells that operate at a very high speed. They are used to
temporarily store data and all arithmetic, logical and shift operations occur in these
registers.

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5
Q

Name 5 Registers.

A

PC - Program Counter
ACC - Accumulator
MAR - Memory Address Register
MDR - Memory Data Register
CIR - Current Instruction Register

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6
Q

What is the PC (Program Counter) ?

A

Register - Holds the address of the next instruction to
be executed.

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7
Q

What is the ACC (Accumulator) ?

A

Register - Stores the results from calculations

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8
Q

What is the MAR (Memory Address Register) ?

A

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

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9
Q

What is the MDR (Memory Data Register) ?

A

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

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10
Q

What is the CIR (Current Instruction Register) ?

A

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

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11
Q

What are buses?

A

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

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12
Q

What are three types of buses?

A

There are three buses in the CPU: data bus, control bus, and address bus.

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13
Q

What are the system buses?

A

There are three buses in the CPU: data bus, control bus, and address bus. These buses
collectively are called the system bus.

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14
Q

What is the width of the bus?

A

The width of the bus is the number of parallel wires the bus has. The width of the bus is
directly proportional to the number of bits that can be transferred simultaneously at any
given time. buses are typically 8, 16, 32 or 64 wires wide.

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15
Q

What is the data bus?

A

This is a bi-directional bus (meaning bits can be carried in both directions). This is used for
transporting data and instructions between components.

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16
Q

What is the address bus?

A

This is the bus used to transmit the memory addresses specifying where data is to be sent
to or retrieved from. The width of the address bus is proportional to the number of
addressable memory locations.

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17
Q

What is the control bus?

A

This is a bi-directional bus used to transmit control signals between internal and external
components. The control bus coordinates the use of the address and data buses and
provides status information between system components.

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18
Q

What are examples of control signals?

A
  • Bus request: shows that a device is requesting the use of the data bus
  • Bus grant: shows that the CPU has granted access to the data bus
  • Memory write: data is written into the addressed location using this bus
  • Memory read: data is read from a specific location to be placed onto the data bus,
  • Interrupt request: shows that a device is requesting access to the CPU
  • Clock: used to synchronise operations
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19
Q

What is assembly code?

A

Assembly code uses mnemonics to represent instructions,
for example ADD represents addition. This is a simplified
way of representing machine code.

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20
Q

What is an instruction divided into?

A

The instruction is divided into operand and opcode in the
Current Instruction Register.

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21
Q

What is OPERAND?

A

The operand contains the data
or the address of the data upon which the operation is to be
performed.

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22
Q

What is OPCODE?

A

The opcode specifies the type of instruction to
be executed.

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23
Q

What is pipelining?

A

Pipelining is the process of completing the fetch, decode, and execute cycles of three
separate instructions simultaneously, holding appropriate data in a buffer in close proximity
to the CPU until it’s required. While one instruction is being executed, another can be
decoded and another fetched.

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24
Q

What does pipelining aim to reduce?

A

Pipelining is aimed to reduce the amount of the CPU which is kept idle. It is separated into
instruction pipelining and arithmetic pipelining.

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25
Q

What is instruction pipelining?

A

Instruction pipelining is separating out the
instruction into fetching, decoding, and executing.

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26
Q

What is arithmetic pipelining?

A

Arithmetic pipelining is breaking down
the arithmetic operations and overlapping them as they are performed.

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27
Q

What is the FDE Cycle?

A

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

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28
Q

What is the fetch stage?

A

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

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29
Q

What is the decode stage?

A

Decode phase:
- The contents of CIR are split into operand and opcode

30
Q

What is the execute stage?

A

Execute phase:
- The decoded instruction is executed

31
Q

What are the three factors affecting the FDE Cycle?

A

There are three factors that affect CPU performance: clock speed, number of cores and
the amount and type of cache memory.

32
Q

What is clock speed?

A

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.

33
Q

What are the number of 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.

34
Q

What is cache memory?

A

Cache memory is the CPU’s onboard memory. 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.

35
Q

What is cache level 1?

A

Very fast memory cells with a small
capacity. (2-64KB)

36
Q

What is cache level 2?

A

Relatively fast memory cell, with a medium
sized capacity. (256KB-2MB)

37
Q

What is cache level 3 ?

A

Much larger and slower memory cell.

38
Q

What is Von Neumann Architecture?

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.

39
Q

What is Harvard Architecture?

A

Harvard architecture has physically separate memories for instructions and data, more
commonly used with embedded processors. This is useful for when memories have
different characteristics
This also allows you to optimize the size of individual memory cells and their buses
depending on your needs.

40
Q

What are the advantages of the Von Neumann Architecture?

A

Cheaper to develop as the control unit is
easier to design.
Programs can be optimised in size

41
Q

What are the advantages of the Harvard Architecture?

A

Quicker execution as data and instructions
can be fetched in parallel.
Memories can be different sizes, which can
make more efficient use of space

42
Q

What is contemporary processing?

A

Contemporary processors use a combination of Harvard and Von Neumann architecture.
Von Neumann is used when working with data and instructions in main memory, but uses
Harvard architecture to divide the cache into instruction cache and data cache.

43
Q

What is a RISC
(Reduced Instruction Set Computer) ?

A

In these processors, there is a small instruction set. Each instruction is approximately one
line of machine code and takes one clock cycle

44
Q

What is a CISC (Complex Instruction Set Computer) ?

A

In these processors there is a large instruction set. The aim is to try and accomplish tasks
in as few lines of assembly code as possible. These instructions are built into the
hardware.

45
Q

What is a multi-core CPU?

A

Multi-core CPUs have multiple independent cores that can complete instructions
separately which results in higher performance.

46
Q

What are parallel systems?

A

Parallel systems accomplish a similar task
however instead of requiring multiple cores they can complete tasks with a single core, by
using threading. Generally, multi-core systems perform better in larger projects than
parallel systems.

47
Q

What is a GPU (Graphic Processing Unit) ?

A

A graphics processing unit (GPU) is a device which unlike CPUs has lots of independent
processors which work in parallel making it very efficient at completing repetitive tasks
such as image processing and machine learning.

48
Q

What is a co-processor?

A

a
secondary processor designed to supplement the activities of the primary processor - GPU

49
Q

What is an input device?

A

An input device is one which can be used to put data and information into a computer.

50
Q

What is an output device?

A

An output device is one which can be used to send information from the
computer.

51
Q

What is optical storage?

A

Optical devices are read from and written to
using lasers. Binary information is represented
by portions of the disc which either reflect or
scatter the incident laser light written in spiral
tracks on the disc’s surface.

A microscopic view of the surface of a CD. The
portions which are recessed, called pits, scatter
light whereas the flat portions, called lands,
reflect light. Pits represent a 0 and lands
represent a 1.

52
Q

What is a CD?

A

CD stands for compact disc. They use optical technology to store small quantities of
information. Most commonly used for audio files, CDs can also be used to store text
and digital images.

53
Q

What is a DVD?

A

DVD stands for digital versatile disc or digital video disc. Similar to CDs, DVDs are
also optical devices which have a higher storage capacity than CDs, making them
suited to storing digital videos which require more storage space than audio files or
photos.

54
Q

What are the characteristics of a CD?

A

CDs are small, thin and light which makes them very portable.

55
Q

How does a Blue-Ray Disc differ to a CD?

A

An advancement over DVDs, blu-ray discs have more than five times as much
storage than traditional DVDs, making them useful for storing high-resolution films.

56
Q

How does magnetic storage work?

A

Devices which store information magnetically represent binary information using two
magnetic states.

57
Q

What are the two types of magnetic storage?

A

Polarised and unpolarised.

58
Q

If a magnetic area is polarised, what happens?

A

If a portion of magnetic material is polarised,
all magnetic poles align and can be read by a read/write head passing over the region.

59
Q

If a magnetic area is unpolarised, what happens?

A

If an area is not polarised, magnetic poles are randomly scattered and produce a different reading on a read/write head. These two states can represent 1 and 0, allowing any
information to be represented in binary form.

60
Q

How does a Hark Disk Drive work?

A

They work by rotating magnetic platters at high speeds
under a read/write head on an actuating arm. The combination of the arm and
rotating platter allows the read/write head to access any part of the platter.

61
Q

How do HDD’s maximize storage?

A

Most HDDs will have multiple platters stacked on top of each other to maximise storage
capacity.

62
Q

What are the disadvantages of HDD’s?

A

Disadvantages of HDDs include their somewhat slow data transfer speeds and their
tendency to become damaged by movement. The combination of brittle platters and moving parts results in a delicate device.

63
Q

What is magnetic tape?

A

First used to record computer data in the 1950s, magnetic tape was a popular
storage medium right through to the 1980s. Wound onto reels, long stretches of
tape were passed through readers which would check the polarity of the tape and
read off a binary value.

64
Q

What are the disadvantages of magnetic tape?

A

Tape was a bulky way to store data, and although
improvements were made by reducing the width of the tape and writing in diagonal
lines as opposed to horizontal tracks, the technology was superseded by more
modern technology like ROM cartridges.

65
Q

What is flash storage?

A

Flash storage is fast and compact. The technology makes use of silicon semiconductors forming the logic gates NAND
and NOR to store electrical charge in one of two states: high or low. These two states represent the binary values True and False, which can be used to represent information.

66
Q

What are Solid State Drives?

A

They are extremely light and portable, while having no
moving parts - this makes them much more resistant to damage from movement
than hard disk drives, which are packed with moving parts. Furthermore, SSDs are
renowned for their high data transfer rates.

67
Q

What are the disadvantages of SSD’s?

A

The primary disadvantage of SSDs is their cost, which continues to decrease as they become more common. Another disadvantage is their limited lifespan. Every time a page is written to, the voltage
required to write to it increases. Over time, this required voltage will become too high for the page to be written to

68
Q

What is Random Access Storage?

A

Random access memory is a type of fast main memory used to store data and
programs that the computer is currently using. This speeds up the computer’s
execution as RAM has higher access speeds than even flash memory.

69
Q

Is RAM volatile or non-volatile?

A

RAM is volatile, meaning that it loses its information when power is lost. For this
reason, RAM isn’t used for storing personal files but as temporary storage while the
computer is running

70
Q

What is Read Only Memory?

A

Read only memory, as the name suggests, cannot be modified. Once programmed,
the state of the memory cells inside does not changed. ROM is useful for storing
fixed sequences of instructions like a computer’s startup (bootstrap) routine. ROM is
non-volatile, so it retains its data even when the computer is powered off.

71
Q

What is Virtual Storage?

A

Virtual storage is the name given to storing information remotely so that it can be accessed
by any computer with access to the same system, for example over the Internet. Examples
of virtual storage include cloud storage services like Google Drive and Microsoft OneDrive
as well as networked storage used in offices and schools.

A-level Computer Science (2 decks)

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