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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
piezoelectric
– 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
3D printers
-solid object is built up using resin, metal or ceramic
27
speakers
- 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
microphones
- 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
keyboard
- allows test input - key press converted into character code - transmitted to a processor - processor displays character on screen
30
screens
- 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
capacitive touchscreens
- 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
resistive touchscreens
- 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
virtual headsets
- 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
sensors
- 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
anti-lock braking system
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
latency
lag in a system egg time to find track on a disk
37
flash memory
a type of EEPROM suited to use in SSDs
38
logic gate
take binary inputs and produce an output
39
logic circuit
several logic gates combined for a specific function
40
NOT
triangle shape if A is TRUE- X is NOT TRUE X = NOT A X = A ̅
41
AND
D shape if A is TRUE and B is TRUE - X is TRUE X = A AND B X = A.B
42
OR
)D shape if A is TRUE OR B is TRUE - X is TRUE X = A OR B X = A + B
43
NAND
Dº shape is A is NOT T or B is NOT T - X is T X = A NAND B X = ̅A.B ̅
44
NOR
)Dº shape if A is NOT T and B is NOT T - X is T X = A NOR B X = ̅A+B ̅ ̅ ̅
45
XOR
))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
truth table
trace the output from a logic circuit all possible input combinations are considered
47
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a - cs (27 decks)

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