3.1.4: Hardware

Control Unit
1. Three main jobs
  1. 1: Decides what instruction to carry out and gets it.
  2. 2: Deciphers the instruction. Works out what needs to be done and carries it out.
  3. 3: Tells other parts of the processors should do to carry out the instruction.
Arithmetic Logic Unit
1. Three main jobs
  1. 1: Does arithmetic (adds numbers together)
  2. 2: Allows for logical decisions to be made. (<, >, etc)
  3. 3: Acts as a gateway between the processor and other parts of the computer. All I/O goes into the ALU until the CU decides what to do with it.
Primary Memory
1. RAM (Memory Unit)
  1. Where everything that the processor uses is stored, including the programs that are running and data used by them.
  2. Also stores the parts of the Operating System that the computer is using at the time.
  4. When computer is switched off all data is lost. This type of memory is called volatile.
  5. Data stored in the hard drive must be moved here before the Control Unit uses it.
  6. Random
  7. Access
  8. Memory
2. ROM
  1. Read
  2. Only
  3. Memory
  4. Non-volatile memory that is not altered.
  5. Performs operations when the computer starts that loads the operating system. These instructions are known as the bootstrap. Once the OS is loaded it can control the computer and so the ROM is no longer necessary. In computers ROM is just used to start the computer up.
  6. ROM chips are incredibly important for machines that only have to perform a set of standard procedures, e.g. a washing machine. The ROM is normally embedded into the device.
3. Memory within the processor
Registers
1. Program Counter
  1. Keeps track of where in memory the next instruction to be executed can be found so that a copy can be placed in the Current Instruction Register.
2. Current Instruction Register
  1. Holds the instruction to be executed whilst it is being executed.
3. Memory Address Register
  1. Holds the address in memory that contains either the next piece of data or an instruction to be used.
4. Memory Data Register
  1. Holds anything that is copied from memory ready for the processor to use it.
5. Accumulator
  1. Multi-purpose, general use registers.
Buses
1. Three main types
  1. Data bus
    1. This bus is used to transfer data from one piece of hardware to another.
  2. Address bus
    1. Carries the address of the location to which the data in the data bus should be delievered.
    2. The Address and the data will systematically travel in tandem towards each bit of hardware. If the hardware recognizes the address it will take the data and if not it will send the data and the address onto the next piece of hardware.
  3. Control Bus
    1. Carries the control signals from the control unit to other parts of the computer.
2. Line down which information passes.
Connectivity methods
1. Physical means
  1. Copper cable
    1. Twisted Copper Pair
    2. Coaxial cable
      2. Many different standards of copper wire from CAT1 - CAT7. Have different characteristics such as different transmission rates, distance over which the signal is reliable and the cost of the cable. Choice of cable based around a compromise between performance and cost.
  2. Fibre-Optic Cable
    2. Rates of data transmission are higher than Copper cable.
    3. Uses light beams sent down a glass filament. Filaments can be wrapped together to provide many channels of communication.
  3. Reliable but restricting as requires physical wires
2. Non-Physical means
  1. Removes the restriction of cables, data can be accessed anywhere that the wireless communication method can reach.
  2. Difficult to control who can access what data. If a company has wireless connectivity method, how do you stop non-employees from accessing the data?
  3. Some people believe that the radio signals may cause health problems. This fear is not proven.
  4. Methods of non-physical communication.
    1. Radio communcation
      1. Used to blanket cover an entire area.
    2. Microwave or infra-red communication
      1. As signals travel in straight lines reduces problems of interception.
      2. Limited to the locations between which data can be sent.
    3. Satellite communication
      1. Used for long distances via a laser or other means of a narrow beam of data.
3. Effectiveness of data communication
  1. Baud rate
    Annotations:
    - This is a measure or the rate at which data can be sent along a means of data transmission. it is measured in bit/s.
  2. Increasing volume of data.
    Annotations:
    - This can be done by sending multiple bits of data at once on different frequencies. The limit to how many frequencies a means of data transmission can handle is called the bandwidth. The higher the bandwidth the more sets of data that can be sent down simultaneously. Copper cables have a low band width, wireless communications have a higher bandwidth and fibre optic cables have the potential for a even higher bandwidth.
Secondary storage
1. Unlike primary storage it is non-volatile (data stays on it when the computer turns off) and has more space.
2. Runs

Next up

3.1.4: Hardware

Description

Resource summary

Media attachments

Similar

	Created by Adam Cook over 9 years ago