System Architecture

System Architecture

1. Internal Components

   • Processors
   • Main memory
   • I/O controllers
   • Buses

2. External Components

   • AKA peripherals
   • Keyboard
   • Mouse
   • Printer
   • I/O devices and ports
   • Secondary Storage
     • USB Drive
     • Floppy Disk
     • CD-R
     • DVD-R

3. Processor

   • 'Brain' of Computer System
   • Fetches and executes instructions
   • Processes data
   • Stores data into main memory

4. Main Memory

   • RAM
     • Found on Motherboard
     • Can be directly accessed by processor
     • Holds data/instructions currently in use by the processor
   • ROM
     • Permanent
     • Non - Volatile
   • EEPROM
     • Elecrically Erasable Programmable ROM
     • Examples include SIM cards
     • Instructions/data can be removed electronically and replaced

5. I/O Controllers

   • Input Output Controllers
   • Used to allow a sharing system (interface) between a hardware device, that is outside of the motherboard, and the processor
   • They are used in:
     • Keyboards
     • Mice
     • Disk Drives
     • VDU - Visual Display Unit

6. System Buses

   • A bus is a set of two or more independant parts of a computer system in order to pass signals between them.
   • 3 types
     • Data Bus
       • Carries out instructions from secondary storage to the processor
       • Bi-directional
       • Data can be read
       • Data can be written
     • Address Bus
       • Carries memory locations from the processor to I/O Devices
       • Uni-directional
       • The processor generates address
       • All data/instructions return via the data bus
     • Control Bus
       • Control Signals go via this
       • Instructs what data will be travelling to and from memory
       • Examples include:
         • Memory Read
         • Memory Write

7. Peripherals

   • A device that isn't directly connected to the CPU
   • AKA i/O Devices
   • Examples include:
     • Mouse
     • Keyboard
     • Printer
     • Hard Disk Drive
     • CD-ROM

8. I/O ports

   • They allow communication from an I/O device to the motherboard and vice versa
   • Used for long term storage of data and instructions
   • Examples include:
     • Hard Disk Drive
     • Solid State Drives
     • Flash Memory
     • DVD-R
     • Blu-Ray

9. CPU

   • Purpose and Function is to fetch, decode and execute

10. Registers

    • Holds short term memory
    • Examples include:
      • MAR - Memory Address Register
        • Says where to get next instructions from
      • Program Counter
        • Says where to get next instructions from

11. Cache

    • Saves frequently used data - helps system run quicker

12. Clock Speed

    • The faster the clock speed, the more instructions can be executed per second