Computer Hardware

Mind Map by lisawinkler10, updated more than 1 year ago
Created by lisawinkler10 over 6 years ago


GCSE Computing Mind Map on Computer Hardware, created by lisawinkler10 on 05/29/2015.

Resource summary

Computer Hardware
  1. CPU
    1. Central Processing Unit carries out all the processing in a computer by fetching, decoding and executing data stored in memory
      1. Arithmetic and logic unit (ALU) carries out the arithmetic and logical operations
        1. The control unit uses electrical signals to control the flow of data within the CPU
          1. All data and instructions are stored in RAM, as binary numbers
          2. The boot sequence is a sequence of processes that contains all the information and instructions to get the computer up and running
            1. The boot loader starts this sequence
              1. After this is completed, control is handed to the operating system to provide the programs for the CPU to process
              2. CPU clock speed is the speed of the fetch-execute cycle (determined by a clock chip)
                1. Clock speed is measured in cycles per second (hertz, Hz) and processor speeds in gigahertz, GHz
                2. The CPU cannot access main memory at the same speed as the processor clock chip; cache memory has access times similar to the CPU speed but is very expensive (located close to CPU with dedicated connections)
                  1. A typical computer has 8GB of main memory but only 2MB of cache memory
                    1. L1, L2 and L3 cache memory refer to how close they are to the CPU
                      1. L1 is often located on the CPU, has a low capacity and runs at the same speed of the CPU, L2 is part of the CPU module, runs close to speed and is usually larger and slower than L1 and L3 is on the motherboard and is larger and slower
                    2. Multi-core processors use multiple CPUs working together so they can all fetch, decode and execute instructions at the same time
                      1. The advantage is more data is processed simultaneously, the disadvantage is more complicated operating systems are needed to manage them
                    3. Memory
                      1. Random access memory
                        1. Volatile (data lost when turned off)
                          1. Can be accessed and changed at any time
                            1. Stores programs and data being used by the computer
                              1. Contains the operating system
                                1. Large (4GB or more)
                                  1. Dynamic RAM needs to be refreshed every few milliseconds and Static hold the charge meaning the data is faster (but design is more complex so more cost)
                                  2. Read only memory
                                    1. Non-volatile
                                      1. Programmed during computer manufacture
                                        1. Stores programs and data being used by the computer
                                          1. Contains the boot program
                                            1. Small (1 or 2MB required for boot program)
                                            2. Virtual memory is part of the hard drive as an extension of RAM (used when computer does not have enough RAM to hold all the data and programs required)
                                              1. Data is passed between RAM and virtual memory but access to virtual memory is slower than RAM so increasing RAM improves performance
                                              2. Flash memory is a type of ROM that can be rewritten (used as a portable memory for storing and transferring data)
                                              3. Secondary Storage
                                                1. Magnetic hard disks store the operating system, installed programs and user data. They are reliable, have a high capacity and low cost
                                                  1. Optical disks transfer files and distribute software. They have a good capacity and are low cost, lightweight and portable
                                                    1. CD and DVD-ROMs are read by lasers
                                                    2. Flash memory consumes little power and has a good capacity (but less than a hard disk), is used in hand held devices and is more expensive
                                                      1. Factors in choosing secondary storage: capacity, speed, portability, durability, reliability
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