structure and functions of processors Flashcards
CPU components
CU, buses, ALU, registers
control unit (CU)
coordinates the activity of all other components
bus
consists of a series of connectors that transfer signals between internal components
system bus
consists of the control,address and data bus
control bus
carries control signals
address bus
carries memory addresses
data bus
carries data
control signals (list)
memory read, memory write, bus request, bus grant, clock
memory read
causes data from the addressed location in RAM to be placed on the data bus
memory write
causes data on the data bus to be written into the address location in RAM
bus request
indicates that a device is requesting use of the data bus
bus grant
indicates that the CPU has granted access to the data bus
clock
used to synchronise operations
arithmetic logic unit (ALU)
performs arithmetic, logical and shift operations
accumulator (Acc)
stores the result of the operation done in the ALU
registers
small amounts of memory in the CPU (therefore fast access) that store a specific piece of information
program counter (PC)
holds the memory address of the next instruction to be executed
current instruction register (CIR)
holds the current instruction, split into opcode and operand
memory address register (MAR)
holds the address in memory where the processor is required to fetch/store data from/to
memory data register (MDR)
holds the data moving between the processor and main memory
accumulator (Acc)
holds the results of the operation executed by the ALU
fetch steps (fetch-execute cycle)
- the address of the next instruction copied for the PC to the MAR
- the instruction held at the address in the MAR in copied to the MDR and the contents of PC are incremented to point to the next instruction
- the contents of the MDR are copied to the CIR
decode steps (fetch-execute cycle)
- the instruction held in the CIR is decoded
- it is split into operand and opcode to determine the type of instruction, additional required data is fetched from memory if required
- and passed to the accumulator
execute steps (fetch-execute cycle)
- the instruction executed and the result is held in the Acc or stored in memory
opcode
specifies the operation that is to be carried out
operand
address of data to be used (this is copied to the MAR) or data to be used (this is copied to the MDR)
words
equal units of memory each of which has a separate memory address
address bus width
determines the maximum possible memory address of the system
data bus direction
bi-directional
data bus width
the number of wires/lines it contains
machine code instruction format
opcode (basic machine operation + addressing mode) + operand
how clock speed affects cpu perfromance
the faster the clock speed the more instructions are fetched, decoded and executed faster
system clock
a series of regular on/off signals used to synchronise the operations of the processor components
rising edge
actions are usually carried out on the rising edge of the clock
factors affecting CPU performance
clock speed, cache size and type, number of cores
how number of cores affects cpu performance
each core is theoretically able to process a different instruction at once
parallel procesing
using several processor cores working at the same time
cache
a small amount of memory on/near the processor (therefor very fast access) that stores data and instructions that have recently been used by the processor (levels 1&2 cache are held on the processor)
level 2 cache
larger but slower than level 1 cache
level 1 cache
split into instruction and data cache, data and instructions are fetched simultaneously
how cache affects cpu performanche
more cache reduces the likelihood of having to fetch from RAM therefore data can be fetched faster
pipelining
a technique used to improve performance by overlapping stages in the fetch-execute cycle or breaking down and overlapping the stages in arithmetic instruction
stored program concept
a program must be loaded to main memory to be executed
von neumann architecture - uses
PCs, laptops, servers, high performance computers
von neumann architecture - storage
data and instructions share the same memory and use the same word length
von neumann architecture - buses
one for data and instructions
von neumann architecture - control unit
one bus is simpler for control unit design
harvard architecture - uses
digital signal processing, microcontrollers, embedded systems
harvard architecture - storage
data and instructions are held in separate memory with different word lengths
harvard architecture - buses
separate buses for data and instructions
harvard architecture - control unit
a control unit for 2 buses is more expensive and complicated
contemporary processor/architecture
desktops have one main memory for data and instructions cache is divided into an instruction cache and data cache thus data and instructions are fetched with harvard architecture
complex instruction set computer (cisc)
a large instruction set is used to accomplish tasks in as few lines of assembly as possible
reduced instruction set computers (risc)
a minimum number of simple instructions, each taking one clock cycle are used to accomplish all the required operations in multiple general purpose registers
CISC - advantages
quicker to code programs, compiler has very little work to translate a high-level language statement into machine code, the code is relatively short thus very little RAM is required to store instructions
RISC - advantages
the hardware is simpler to build with fewer circuits needed for carrying out complex instructions, pipelining is possible as each instruction takes the same amount of time, risc use of ram allows better performance processors at less cost
multicore processor
able to distribute workload across multiple processor cores, thus achieving significantly higher performance by performing several tasks in parallel
co-processor
an extra processor used to supplement the functions of the primary processor (CPU)
graphics processing unit (GPU)
a specialised electronic circuit consisting of thousands of small efficient cores, which is very efficient at manipulating computer graphics and image processing
input devices
transfer data from an external source to the computer
manual input devices
keyboards, pointing devices, microphones, touch screens
barcode systems
UPC-A, code 128
universal product code version A (UPC-A)
can only represent numeric digits, used in retail and warehousing
code 128
can represent letters and numbers, used in transport and shipment tracking
quick response (QR) codes
2D barcodes and can be read by smartphones or tablets
2D scanners
used to convert a hard/paper copy document/photo into a computer readable format
3D facec recognition
specialist software measures and compares the proportions of a face with those stored
3D scanners
many rely on tomography (to image something in very thin slices)
sensors
a hardware device that can take measurement of physical properties from real world surroundings
monitor
values are reported but no changes are made
control
process of operations and value of the next input can be altered and the output can affect the next input
detection systems
monitor intruders stepping near windows/values with pressure sensors
pick up the sounds of breaking glass/footsteps with acoustic sensors
pick up movement/changes in temperature with infra-red sensors
monitoring systems
user first activates system with a PIN or placing alarm fob near a receive
sensors constantly monitor the rooms
data is converted to digital form with an ADC and is sent to microprocessor
output devices
convert computer produced data to a readable form
inkjet printers
small, inexpensive, ink prices are marked up
laser printers
use dry powdered ink (toner), used in businesses, fast and reliable, good print quality
dot matrix printers
strike an inked ribbon which inprints dots to form letters on a page, used where multi-part stationary is needed, effective in damp and dirty atmospheres, noisy, poor print quality, expensive
3D printers
can print intricate objects with hollow areas using plastic filament,powdered resin, ceramic, metal or paper
medical applications of 3D printers
manufacturing prosthetics/orthodics, reconstructive surgery, general surgery
artistic applications of 3D printers
prototyping
manufacturing applications of 3D printers
manufacturing parts for cars
radio frequency ID (RFID)
powered receiver emits radio frequency energy, transponder antenna becomes energised, transponder can send data to receiver
uses of RFID
security controls or identifying people, animals, goods or values, shipping and supply chain tracking for goods
passive tags
have no power source, rely on radio waves from the receiver, need to be close to receiver
active tags
use a larger buttery powered beacon can broadcast its own signal to receivers from up to 300m away
actuators
motors commonly used with sensors to control a mechanism
speakers/headers
digital data is sent to a DAC, the signal is then boosted with an amplifier
liquid crystal display (LDC) screens
contain groups of red, green and blue diodes to form each pixel, these screens need backlighting using CCFLs or LEDs as they don’t emit light
LEDs over CCFLs
LEDs reach max brightness near immediately, LEDs produce sharper images, LEDs produce brighter light thus better picture definition, LEDs are smaller so screens can be thinner
organic LED screens
plastic thus more flexible, brighter, thinner and lighter, less power consumption, larger field of view
multimedia light projectors
compact, high resolution, full colour projectors, converts video signal into a viewable image and projects it on a screen
random access memory (RAM)
stores OS, running programs and data in use, volatile, read/write
read only memory (ROM)
bootup instructions, non-volatile, read only
virtual memory
a part of the hard drive used as a RAM extension
magnetic storage (HDD)
concentric tracks are created on a magnetic disk, the disk spins quickly, spinning platters are each read by disk heads, data is read/written as a sector moves under the head
HDD - properties
fast read/write speeds, relatively cheap per TB
solid state storage
commonly use non-volatile flash memory
SSD - properties
durable, consume less power, more portable, more expensive than HDDs, very fast access speed
USB flash drives - properties
max capacity: 128Gb, prices start low, can use password protection, useful for data transfer
optical disks - properties
cheap to manufacture and distribute, robust during carriage, light weight, suited for software mailing, have medium access speed
optical disk formats
read only (ROM), recordable (R), re-writeable (RW)
CD-ROM uses
software distribution
CD-R uses
copying games, software, audio/video files, documents
CD-RW uses
short/medium term backup or file transfer
DVD/BluRay uses
films
CD-ROM capacity
700MB
DVD capacity
4.7GB - 8.5GB
BluRay capacity
25GB - 50GB
SSD capacity
4GB - 2TB
HDD capacity
512GB - 6TB
