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OCR A Level Computer Science > Hardware and Circuits > Flashcards

Hardware and Circuits Flashcards

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1
Q

What is an ADDER

A

a circuit which carries out all four rules of binary addition.

Made by wiring two half- adders together and adding a third input as well as an OR gate.

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2
Q

what is a HALF ADDER

A

only carries out the first three rules of binary addition (no carry bit).

XOR gate - sum
AND gate - carry

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3
Q

What is a flip- flop

A

a “bi- stable” circuit (has 2 stable states)
used to hold a single bit in memory

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4
Q

D - type flip - flop

A

Holds a signal - typically an input signal. It releases the signal when the clock pulse comes by.

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5
Q

what are the types of inputs and how are they used to plot outputs

A

Inputs: Data signal and Clock signal

Plot the data level (high or low) at the rising clock signal, and join these to give the output signal.

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6
Q

Which three Components of the Processor are involved in the FDE cycle

A

RAM
CU
ALU

the CU and ALU are both within the CPU

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7
Q

How are signals passed between the RAM, CU and ALU

A

Using the Adress bus, Data bus and Control bus

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8
Q

What are Buses?

A

Communication channels that link parts of the CPU

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9
Q

What is Parallel transmission and where is it used?

A

Bits are sent together along parallel channels. THis is faster but requires extra space.

Used within the CPU

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10
Q

What is serial Transmission and when is it used?

A

Bits are sent one after the other, this is slower

Used by USB to connect two devices

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11
Q

Address Bus

A

Sends adress of a memory location to RAM during fetch and save operations

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12
Q

Data Bus

A

Sends data and instructions to and from ram during fetch and save operations

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13
Q

Control bus

A

Sends control signals from the CU telling other parts of the computer what to do

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14
Q

Registers

A

Small areas of high speed memory within the CPU

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15
Q

What does the PC/ Program Counter do

A
  • Counts through the lines of the program, storing the address of the next instruction + copying it to the MAR
  • Increments by one each cycle
  • Can be overwritten using branch commands
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16
Q

MAR

A

stores the address for fetching or saving data

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17
Q

MDR

A

stores the data/instructions being fetched or saved. It acts as a buffer as instructions are copied to the CIR

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18
Q

CIR

A

takes the instruction code from the MDR to be decoded.

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19
Q

Summarise the Fetch phase in terms of processor components

A

Data and instructions go from the RAM to the CU

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20
Q

Summarise the Decode phase in terms of processor components

A

The CU turns the code into a control signal which is sent to the ALU

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21
Q

Summarise the Execute phase in terms of processor components

A

the ALU carries out the command

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22
Q

Describe the Fetch phase of the FDE Cycle

A

-The address of the next instruction is copied from the PC to the MAR
- A read signal is sent via control bus
-the contents of the MAR are sent accross the address bus to RAM
- the instruction held at that address is copied to the MDR by the data bus. Simultaneously, the PC increments by 1.
- The contents of the MDR are copied to the CIR

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23
Q

Describe the decode phase of the FDE cycle

A
  • within the CIR, the instruction is split into an operator and operand
  • it is decoded and turned into a control signal, which is sent from the CU to the ALU via control bus
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24
Q

Describe the Execute phase of the FDE cycle

A
  • The appropriate instruction is carried out on the operand in the ALU
  • The result is stored in the accumulator.
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25
Q

How is the result of an operation saved?

A

The ALU copies the result to RAM

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26
Q

How are data and instructions stored in Von Neuman Architecture?

A

Together in RAM as binary numbers

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27
Q

How are data and instructions stored in Harvard Architecture?

A

RAM is split into 2 partitions for data and instructions to be stored seperately

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28
Q

How are data and instructions stored in Contemporary/ Modern Harvard Architecture?

A

Together in RAM as binary numbers

29
Q

How many buses are used for data and instructions in Von neuman architecture

A

has a RAM, CU and ALU joined by buses

There is one bus used for data and instructions (the data bus)

Therefore it takes 2 FDE cycles to complete a command

30
Q

How many buses are used for data and instructions in Harvard Architecture

A

Two seperate buses

31
Q

How many buses are used for data and instructions in Contemporary/ Modern Harvard Architecture

A

Two seperate buses

32
Q

Compare the three types of processor architecture: Von Neuman, Harvard, Contemporary/ Modern Harvard

A

Von Neuman: Flexible but slow
Harvard : Faster but Inflexible
Contemporary : Best of both

33
Q

What is an Instruction Set

A

a list of all instruction codes known by the processor

34
Q

what is CISC and it’s attributes

A

Complex Instruction Set Computer

  • Has a large instruction set (some rarely get used)
  • each instruction long and detailed
  • may take several cycles to carry out an instruction
  • only a few lines to write a program
  • Requires more power (larger battery)
  • Generates more heat (cooling mechanisms)
  • More expensive complicated circuits
35
Q

what is RISC and it’s attributes

A

Reduced Instruction Set Computer

  • Short and simple instruction set
  • each code does 1 simple task
  • takes ~1 cycle to carry out 1 instruction
  • Takes many lines to write a program
  • may require greater RAM due to program size
  • Requires more complex compiler
  • small slim processor
36
Q

Compare RISC and CISC

A
  • neither is faster than the other
  • CISC software cannot be run on a RISC computer
  • RISC better suited due to mobile devices due to small size, cheapness, use of less power and less heat produced.
37
Q

7 factors affecting processor performance

A
  • Clock speed
  • Word length (size of bus and registers)
  • Cache size
  • Amount of RAM
  • co - processor/ graphics card/ SIMD
  • pipelining
  • multi- core/parallel processing / MIMD
38
Q

what is pipelining

A

-One instruction is fetched while another is being decoded and another is executed.
- Concurrent processing of multiple instructions
- only works if instructions aren’t dependent

39
Q

what is parallel processing

A

the use of a multi - core processor (MIMD) that can process several instructions concurrently.

Can only happen if the instructions aren’t dependent

40
Q

Which 2 types of computer can’t use pipelining?

A
  • CISC
  • Von Neuman
41
Q

what is SIMD

A

Single Instruction Multiple Data

the processor fetches and decodes an instruction once, then it carries out the single instruction multiple times, processing many data items in the same way.

42
Q

what are SIMD sub- processors / co- processing

A
  • a group of small processors carrying out the same instructuon at the same time
  • very fast way to process a large amount of data
43
Q

what is a GPU or graphics card

A

Specialist hardware add- on that processes images very rapidly using SIMD/ co- processor.

Can be used for other tasks than graphics eg. bitcoin

44
Q

what is MIMD or multi- core processing

A
  • Multiple instruction , multip;e data
  • a group of processors work together, carrying out different instructions.
  • a shared block of memory holds the instructions and data
45
Q

list advantages and disadvantages of MIMD

A

+ uses less energy
+ generates less hear
+ speed advantage
- task dependency
- complex software design

used in almost every modern computer

46
Q

list advantages and disadvantages of SIMD

A

+ fast processing
+ process large amounts of data
- dependencies between data
- varied processes

47
Q

what is input

A

conversion of data into digital electronic form prior to processing

48
Q

list 4 types of input

A
  • user input
  • image processing
  • digital signal processing
  • sensors
49
Q

when should manual input be used + give an example

A
  • input is varied
  • speed not as important as flexibility
  • no special equipment available

eg. mouse , keyboard

50
Q

when should automated input be used + give an example

A
  • input is structured
  • input is repetetive
  • speed is important

eg. barcode, chip and pin

51
Q

when should sensor input be used + give an example

A
  • input is detectable by sensors
  • must be monitored without breaks
  • input takes place where there is no human operator

eg. temperature, pressure

52
Q

how do input devices convert analogue to digital

A
  • analogue measurements vary continuously. examples include temperature and sound waves.
  • input devices sample the value many times a second
  • each sample is recorded as a digital value
53
Q

how to acheive high quality digital recordings from an analogue input such as sound waves.

A
  • sample the signal frequently
  • store variations precisely
54
Q

what does an accelerometer measure

A

start of a movement, a change in velocity, change in direction of motion.

they can be found in most mobile phones.

55
Q

what is a RFID

A

Radio Frequency Identification Tag.
- attatch or implant into products or even living creatures.
- when the chip is scanned you can identify or locate the tag and hence the object.
- an “active” tag also has a battery which broadcasts radio waves

56
Q

explain how code number size is related to the quality of analogue input and outpit

A

the bigger the number is, the more precise the stored information is.

eg. 10 degrees vs 10.2 degrees.

57
Q

what is CAD/ CAM
explain it’s input, processing and output

A

computer aided design/ manufacture

Input - use 3D toolsets with mouse or touch screen
processing - replace blocks, compare drawings, count objects
Output - 3D print or Display on screen

58
Q

give 4 attributes of robotics

A
  • combine sensors with actuators
  • independent processing
  • self- moving
  • mostly do not look like humans
59
Q

what is the difference between memory and storage.

A

memory: electronic, currently in use

storage: non- electronic, not in use

60
Q

ROM

A

read- only memory

used for boot instructions

wired in permenantly at factory

61
Q

RAM

A

-volatile electronic memory used in normal operations

  • can access any location in one step
62
Q

Cache

A

small amount of fast access memory that stores frequently used instructions

63
Q

Virtual memory

A

Storage used as memory

64
Q

Describe Magnetic storage and give a pro and con

A

magnetic disk coated with iron particles. electricity magnetises the particles. North and south represent 1 and 0.

High capacity but not portable.

65
Q

Describe optical storage and give a pro and con

A

a laser burns tiny pits into the surface of a plastic disk
presence or absence of a pit represents 1 or 0

Inexpensive , but can only be written once.

66
Q

Describe flash or SSD storage and give a pro and con

A

electrons carry negative charge.

Light, portable, high capacity and fast
but is more expensive

67
Q

ALU

A

holds results of calculations from ALU
holds all input / output

68
Q
A

OCR A Level Computer Science (16 decks)

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