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a - cs > 3 - hardware > Flashcards

3 - hardware Flashcards

1
Q

primary memory

A

can be accessed directly from the CPU

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2
Q

RAM

A

Random Access memory
- can be written to and read from
- stores files/ data currently in use
- volatile (memory contents are lost powering off the comp)
- can increase size to improve operational speed

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3
Q

ROM

A
  • non volatile
  • permanent memory (can’t change contents)
  • stores data the comp uses when powering up (BIOS/ bootstrap)
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4
Q

DRAM

A

dynamic RAM
- capacitors hold the bits of information
- transistors act like switches and allow chip to control circuit to read/ write the capacitor
- needs to be refreshed constantly - if not charge will leak away leaving it with 0
+ cheaper
+ consume less power
+ higher memory capacity
used by main memory

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5
Q

SRAM

A

uses flip flops which hold each bit
+ doesn’t need to be refresehd
+ faster
- if accessed at a high freq power usage can exceed a DRAM
memory cache generally uses SRAM for this reason

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6
Q

PROM - Programmable ROM

A
  • can be altered once
  • made of a matrix of fuses
  • uses electric current - burns fuses to alter specific cells
    eg mobile phones, RFID tags
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7
Q

EPROM - Erasable Programmable ROM

A
  • use floating gate transistors and capacitors not fuses
  • UV light programs it through a quartz window
    eg new games consoles, apps under development
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8
Q

EEPROM -electrically erasable programmable ROM

A
  • electrical signal can be used to remove existing data
    + chip can remain in the circuit while contents are changed
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9
Q

buffers

A
  • ## temporary storage for data transmitted from one part of the system to another which functions as a queue
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10
Q

embedded systems +

A

+ small so easy to fit
+ low cost
+ dedicated to one task - simple interface - no OS
+ consume little power
+ very fast reaction to changing input
+ mass production so reliable

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11
Q

embedded systems -

A
  • difficult to upgrade devices - with new tech
  • fixing it is specialist
  • interface can be simple but in reality it can be confusing
  • open to hackers and viruses
  • due to difficulty in upgrading and fixing devices are throw away - wasted
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12
Q

embedded system

A

A computer system with one dedicated task ( no multitasking)
hard for the user to update
built in hardware and software

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13
Q

magnetic storage - HDD

A
  • has platters - that spin
  • has read/write arm
  • data stored on surface in sectors and tracks
  • magnetic field determines binary value
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14
Q

latency

A

time it takes for a specific block of data on a data track to rotate around to the read-write head

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15
Q

removable hard disk drives

A

are HDDs that are external to the comp and can be connected to the comp using a USB port

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16
Q

magnetic storage +/-

A

+ large storage
+ cheap
+ fast read/write
- lots of parts
- not durable
- sealed unit ( cant fix easily)
- not portable

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17
Q

solid state storage - SSD

A
  • sends current which forces electrons through a barrier
  • and traps them in floating gates
  • binary data is stored by the held electrons
    (flash memory)
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18
Q

SSD +/-

A

+ reliable - no moving parts
+ lighter
+ less power consumption
+ run cooler than HDDs
+ access data faster
- expensive
- unknown longevity

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19
Q

optical storage - CD DVD

A
  • is a disk - with a spiral track
  • binary represtented using pits/lands
  • laser shines on - pits reflect light differently to determine binary value (read)
  • laser makes indents on disk (write)
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20
Q

dual layering

A

used in DVDs to increase storage capacity
2 layers which are joined together
- shorter the wavelength of laser light the greater the storage capacity of the medium
- can cause birefringence (light is refracted into two beams causing reading errors)

21
Q

blu-ray

A
  • uses blue laser (shorter wavelength)
  • blue light means pits and bumps can be much smaller (can store more)
  • uses a single thicker disk - no birefringence
  • automatically come with encryption
22
Q

laser printers

A
  • use dry powder ink and static electricity
  • ## use blue cyan magenta black - print all in one go
23
Q

inkjet printers

A
  • nozzles spray ink onto paper
  • has a stepper motor and belt which moves the print head across the page
  • a paper feed which feeds the printer with pages as required
  • thermal bubble of piezoelectric
24
Q

thermal bubble

A
  • tiny resistors create localised heat which makes the ink vaporise
  • causes the ink to form a tiny bubble, as the bubble expands some of the ink is ejected from the print head onto the paper
  • when the bubble collapses, a small vacuum is created which allows fresh ink to be drawn into the print head
  • this continues until the printing cycle is completed.
25
Q

piezoelectric

A

– a crystal is located at the back of the ink reservoir for each nozzle
- The crystal is given a tiny electric charge which makes it vibrate
- This vibration forces ink to be ejected onto the paper and at the same time more ink is drawn in for further printing.

26
Q

3D printers

A

-solid object is built up using resin, metal or ceramic

27
Q

speakers

A
  • passed through DAC
  • passed through amplifier to create larger current
  • electric current is then fed to speaker
  • current fed into wire - wire wrapped round core - interacts with magnet
  • vibrates creating sound waves
28
Q

microphones

A
  • diaphragm in the mic vibrates
  • coil is wrapped around magnet - coil is connected to the diaphragm using a cone
  • cone moves in and out causing the copper coil to move backwards and forwards.
  • causes the magnetic field around the permanent magnet to be disturbed, inducing an electric current.
  • current is then either amplified or sent to a recording device
29
Q

keyboard

A
  • allows test input
  • key press converted into character code
  • transmitted to a processor
  • processor displays character on screen
30
Q

screens

A
  • use LCD backlit with LED or OLED (organic light emitting diode)
  • OLED - give off light when electricity applied to electrodes
  • each screen pixels is made up of 3 sub pixels RGB
31
Q

capacitive touchscreens

A
  • made up of layers of glass acting as a capacitor creating electric fields between glass layers
  • When the top layer is touched, the current changes - location is calculated by microprocessor
    + medium cost
    + good visibility
    + multi touch
    + durable
  • only allows bare fingers
32
Q

resistive touchscreens

A
  • makes use of upper and bottom layer
  • when touched layers touch making complete circuit
  • signals are sent out which are interpreted by microprocessor
    + cheap
    + can use any touch - bare, gloved fingers
  • poor visibility
  • no multi touch
  • not durable
33
Q

virtual headsets

A
  • video sent from a comp to headset
  • two feeds are sent to an LCD/OLED - one for left and right - lenses reshape video making it 3D
  • when user moves head sensors measure movement
  • use binaural sound (surround sound
  • some use infrared sensors to monitor eye movement
34
Q

sensors

A
  • are input devices which read or measure physical properties such as temp pressure acidity etc.
  • uses ADC - converts physical values into digital values
  • microprocessor analyses data
  • if outside acceptable range alarm is raised or signals sent to control valves
35
Q

anti-lock braking system

A

use magnetic field sensors to stop the wheels locking if they have been applied too sharply
- when one of the car wheels rotates too slowly data is sent to microprocessor
- checks rotation of other wheels - changes it to match others
- constantly being checked to prevent locking

36
Q

latency

A

lag in a system egg time to find track on a disk

37
Q

flash memory

A

a type of EEPROM suited to use in SSDs

38
Q

logic gate

A

take binary inputs and produce an output

39
Q

logic circuit

A

several logic gates combined for a specific function

40
Q

NOT

A

triangle shape
if A is TRUE- X is NOT TRUE
X = NOT A
X = A ̅

41
Q

AND

A

D shape
if A is TRUE and B is TRUE - X is TRUE
X = A AND B
X = A.B

42
Q

OR

A

)D shape
if A is TRUE OR B is TRUE - X is TRUE
X = A OR B
X = A + B

43
Q

NAND

A

Dº shape
is A is NOT T or B is NOT T - X is T
X = A NAND B
X = ̅A.B ̅

44
Q

NOR

A

)Dº shape
if A is NOT T and B is NOT T - X is T
X = A NOR B
X = ̅A+B ̅ ̅ ̅

45
Q

XOR

A

))D shape
X= 1 if (A is 1 AND B is NOT 1) OR (A is NOT 1 AND B is 1)
X = A XOR B
X = A ⊕ B

46
Q

truth table

A

trace the output from a logic circuit
all possible input combinations are considered

47
Q
A
48
Q
A

a - cs (23 decks)

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