4.7: section 5: computer organisation and architecture Flashcards
name 6 internal components in the central processing unit
- processor: Responds to and processes the instructions that drive the computer.
- main memory: stores data and instructions that are to be processed
- address bus: -sends the memory address of a word from the processor to CPU components
- control bus: Sends control signals/lines between the I/O controllers and the processor
- data bus: -sends data and instructions between CPU components
- I/O controller: receive input and output requests from the processor and send device specific controls signal to the device
what is von Neumann architecture
- instructions and data must be stored in the main memory to be executed
- the machine code instructions are fetched from the memory one at a time using the same bus and decoded and executed by the processor
used extensively in general purpose computing systems
what is Harvard architecture
- has separate memories for data and instructions
- has separate buses for data instructions
- used embedded Digital Signal Processing (DSP)
- faster than Von Neumann as the instruction and data can be fetched at the same time
what type of systems use Harvard architecture
- used with embedded digital signal processing
- embedded systems include special purpose built in computers which operate in real time
- e.g. traffic lights, navigation systems, aircraft flight control systems
what is the stored program concept
2 points
machine code instructions stored in main memory are fetched and executed serially by a processor that performs arithmetic and logical operations.
what is addressable memory
4points
Memory is divided into units called words.
Word: a fixed size group of digits, typically 8, 16, 32 or 64 bits
- Each word has its own specific memory address
- when a processor wants to read a word of data from the memory it puts the address of the word onto the address bus
what is a processor instruction set
-the group of instructions that a processor can carry out.
-Each type of
processor has its own instruction set, so instructions for one processor may not be
compatible with other processors.
-usually stored in machine code
what are the 6 typical instructions included a processor instructions set
- data transfer
- arithmetic operations
- comparison operators
- logical operators
- branching
- halt
what is opcode
- the operation code which corresponds to an instruction
- this will include the addressing mode
what is the operand
-the data value the operation is acting on
what is immediate addressing
-where the value represented in the operand is the actual data value
what is direct addressing
-where the value represented by the operand is the memory address holding the data
what are barcodes and the two types
printed diagrams made of light and dark portions which contain information computers can read with a barcode reader.
there are 1d and 2d barcodes
how do 2d barcodes differ
contain more information in the same amount of space but require more processessing to extract content
what are barcode readers made up of
laser light source
lens
photodiodes
mirror
how do barcode readers work
MLPLP
- mirror directs light from the laser onto the barcode
- light reflected by barcode passes through lens and is incident on the photodiode
- photodiode turns light into electrical charge which can be measured and processed to form a digital signal
- light portions of diode reflect most light wile dark portions absorb
- pattern of light and dark stripes in barcode correpsponds to inary 1s and 0s
what are digital cameras made up of
lens sensors: CMOS, CCD cells shutter filter-coloured cameras
how do digital cameras work
LSCS F
- lens focuses light onto sensor
- sensors convert light into electrical charge
- sensors are made up of cells which represent pixles in the final image
- shutter regulats the path of light between the light and sensor
- in colour cameras there are multiple cells per pixel
- each cell has a filter that only allows a certain wavelengt of light.
- bayer filters have the same number of green, blue and red filters that let cameras produce images close to what the human eye sees
what are laser printers made up of
laser light source mirror drum toner roller fusers
how do laser printers work
DLI TN TP F
- drum is positively charges
- e laser is directed at its surface by the mirror. Areas on which the laser is incident are discharged,
- this leaves an impressions of the page in electrical charge
- toner roller dispenses negatively charged toner onto the drum
- toner is attracted to positively charged portions of the drum and is applied to paper
- paper is heated by fusers which fixes toner to paper
- colour printers use the same process but have 4 colours of toner CYMK
what are RFID tags made up of
chip with a small amount of memory
coil of wire attachted to chip/antenna
what are RFID tags for
radio frequency tags are a method of tranferring information wirelessly between a taga and a reader
what are two types of RFID tags
passive: inducing enough power form reader to operate chip
active: contain a small ower supply like a battery
they can be read from much further away than passive tags
how do RFID tags work
RPAD
- reader emits radio waves which are picked up by tags antenna
- power induced from these waves is enough to power a passive tag’s chip
- the chip uses its antenna to emit a radio wave containING its information
- the wave is picked up by the reader hich decodes the information
what type of sotrage is primary storage
volatile RAM and ROM
what type of storage is secondary storage
non volatile storage is used to store files and applications
what are hard disk drives
a secondary storage device made up of a number of circular platters from a magnetic material
they are typically between 500GB and 5TB
they are suseptible to damage form movement
how do hard disk drives work
APADR
- above each platter hovers an actuating arm where the read/write head is mounted
- the read/write head changes magnetic polarity of parts of the platter
- the actuating arm allows the read/write head to access all parts of each platter
- data is written in concentric track-each is divided into sectors
- the platter rotates thousands of times per minute allowing good read/write speeds
how can you increase hard disk drive capacity
add more platters
decrease width of tracks
what are solid state drives
a secondary storage device mad of non volatile NAND flash memory cells and a controller
not capable of overwriting data so it must be completely erased to write new information to it
has no moving parts
how is information stored on solid state drives
- memory cells are formed of floating gate transistors which store information by trapping electical charge
- data is stored in pages which combine to make blocks
what are optical disks
secondary storage in the form of CDs, DVDs and Blue-Ray which can be read optically by laser
they can be read only, recordable or rewritable
they have one continuos track that sprials from the disk centre
how do read only disks work
SBPC
- stores data using pits and lands
- pits are burnt into the disk with a high powered laser
- a low powered laser beam is passed over the surface
- when the laser passes a land the beam is reflected onto a photodiode
- when the laser passes a pit the beam is scattered
4.the pattern of reflections and scatters can be converted into digital signals
how do recordable and rewritable disks work
ORAP
- a pattern of reflectionsa and scatters is created by an opaque dye on the disks surface
- if there is no dye the beam is reflected of the optical disks surface
- if there is dye the laser beam is absorbed
- recordale disks use a photosensitive dye which changes form opaque to transparent under a high powered laser
