Hardware and Communications

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  • Created by: Schofe98
  • Created on: 01-06-17 15:20

Components of a Processor

Arithmetic Logic Unit - repsonsbile for all calculations and logic operations.

- can act as a conduct for input and output to and from the processor

Control Unit - manages the execution of machine code by sending control signals

Registers - small blakc of memory which is used as temporary storage for instructions as they are being processed.

- program counter

- memory address register

- memroy data register

- current instruction register

- Accumulator

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Components of a Processor

Arithmetic Logic Unit - repsonsbile for all calculations and logic operations.

- can act as a conduct for input and output to and from the processor

Control Unit - manages the execution of machine code by sending control signals

Registers - small blakc of memory which is used as temporary storage for instructions as they are being processed.

- program counter

- memory address register

- memroy data register

- current instruction register

- Accumulator

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Registers

Program Counter - stores the address for the next instruction to be executed

Memory Address - contains the address of the instruction or data to be fetched next

Memory Data - contains the data or instruction that has been fetched.

Current instuction register - holds a copy of the instruction that has been fetched for executing

Accumulator - any instruction that performs a calculation make use of this.

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Memory and Caching

L1 - extremely fast but relatively small.

usually embedded within the Central processing unit.

L2 - often has a higher capacity than L1 and as a result operates slower

Maybe located on the CPU, dedicated to single or pairs of cores, or located on a seperate chip to avoid becing slowed by traffic of main buses.

L3 - works to improve the performance of L1 and L2 cache.

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Parallel Processing

Two or more processors work together to perform a single task

  • the task is split into subtasks (threads) which are executed simultaneously by available processors.

Advantages: 

  • More instructions can be processed in a shorter time because they are being executed simultaneously.
  • Tasks can be shared to reduce load on individual processors and avoid bottlenecks.

Disadvantages:

  • difficult to write programs for multi core programs
  • results from different processors need to be combined at the end of processing, which can be complex and adds time.
  • not all tasks can be split acorss multiple processors
  • concurrency introduces new classes of software bugs.
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FETCH - DECODE - EXECUTE

Single processor can only execute a single instruction at a time.

1. Fetch - fetches the data and instructions from main memory then stores them in its own internal registers.

2. Decode - the CPU 'understands' the commands within the instructions using an instruction set.

3. Execute - data processing and then stores in another register.

Once finished one cycle, the CPU will start the next cycle.

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Memory and Caching

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Input and Output Devices

Optical character recognition – converts printed media into editable text documents using a scanner.

  • OCR is a post processing step that performs pattern matching by scanning the image for shapes that it can recognise as letters, numbers and symbols.
  • Easy for humans to read, but complicated for the computer

Optical mark recognition – A reader reads forms to detect black lines and marks and note the position on the page.

  • Used in predefined forms
  • Multiple choice exam and registers, as they can be automatically marked and processed.
  • Not suitable for written communication

Magnetic ink recognition – combination of ink containing iron oxide and specific fonts so it can read by a MICR reader.

  • Normally just used in cheques.
  • Doesn't have to rely on OCR which can be problematic.

Touch screens - resisitive and capacitive, both versions send X and Y coordinates of the touch when touch is registered.

  • Resistive touch screens are much cheaper and are made up of two transparent sheets which send a voltage when they touch.
  • Capacitive allow for much sharper image and for multiple touch points to be recorded simultaneously and making them more expensive.
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Secondary Storage

Magnetic storage devices - a hard drives is a high capacity stoage meduim.

  • has a fast transfer rate and access time
  • provide a good compromise between stoage capacity, performance and cost.
  • hard drives stores data on a hard drive plater; data is read and saved using an arm that has a special read/write head.

Flash storage - Solid state drives are becoming more popular as they tend to have a better performance than hard drives

  • Tend to be more expensive
  • No spinning disk or moving read head

Optical drives – using lasers to store data by burning microscopic indentions into a disk such as a CD.

  • On DVDs data is stored on two levels and there are two lasers on different wave lengths used to read the data.
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Fragmentation and Defragmentation

Files become fragmentated meaning they are split and stored on different parts of the disk.

  • Takes a lot longer to collect data which is widely fragmented

Defragmentation is the process where files are physically re-arranged so that they are no longer fragmented and parts are stored together.

  • Improves the speed of accessing data
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Networks

Networking standards are what underpin communications.

A distibution system is where comptuers work together by sharing services with one another to provide a complete system.

  • The internet is a worldwide communications intfrastructure, which means that you can access websites in any country in the world.

Client server - services are made available on servers to which clients connect in order to access the services eg Web Servers.

Peer to peer - each computer has the same status as the others.

  • No computer acts as a server, meaning that peers must work togerther to fulfil the required task eg file sharing.
  • Allows very large files to be downloaded efficiently without need for a powerful server.
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Protocols

A set of rules that governs communications. A number of protocols together make a protocol stack.

HTTP: allows resources to be transmitted over the network.

FTP: works on an interactive model and is used when copying (uploading or downloading) a file from one location to another via the internet.

SMTP: standard internet for electronic mail transmission.

TCP: (transmission control protocol) provides relaiable and error checking streams of packets over a network and is the core transport protocol for HTTP.

IP address: each computer must have an unique address to the data is sent to the correct machine over the internet.

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Networking

Hand shaking - to set up a communication link, both devices need to agree on a set of protocols to use.

  • Signal from one device to the other and is ackowledged by the second.

Router - routes the packets to the correct port.

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