Internal Hardware Components of a Computer

Internal Hardware Components of a Computer

1. Main Memory

   • RAM
     • Random Access Memory
     • Read only memory, it stores data and can be read from but not written to. So must only accept data from the data bus.
     • The data is stored electronically on chips made up of millions of cells each of which has its own unique address. Each cell can contain either an instruction or data
       • The cells can be accessed as they are needed by the processor, by referencing an address
     • Volatile - When you turn off the computer ass the contents of the RAM are lost
     • Whenever a program is run on your computer the entire program or parts of it are loaded into RAM. The more RAM you have, the more applications you can have running at the same time
   • The main memory is used to store data and instructions used by the processor
   • ROM
     • Read Only Memory
     • Stores data that can be read from, but not written to, e.g. BIOS
       • BIOS stores the instructions needed to startup the computer
     • Non Volatile - When the computer is turned off the contents are not lost
     • Can get programmable ROM which can also be written too
   • Addressable Memory
     • Memory is made up of addressable cells which store the various instructions and programs in them. Each cell is uniquely identified by an address.
     • The memory is organised in a systematic way, the cells being organised into memory blocks. This helps the processor find the data it is looking for quicker.
       • A memory map can be produced which shows which programs are stored at which address.
     • Memory addresses are normally shown in hex

2. Bus

   • A bus is a microscopic wire that transmits data between the internal components of a computer. Data is passed along the wires allowing the processor and other components of a computer (e.g. the Random Access Memory) and allows them to work together.
   • Data Bus
     • Transfers data between the processor and the memory and the I/O controllers
     • The data bus is bi-directional so data can be passed both ways down it.
     • The speed of the data bus depends on the amount of wires in it.
     • When large items of data are sent they are split up into smaller parts and sent one after each other
   • Address Bus
     • Used to specify a physical address in memory so that the data bus can access it. The processor is the only component that can place addresses on the bus.
     • This bus is the only unidirectional bus, meaning data can only be passed down it one way
     • The addresses for memory the processor requests is sent down the address bus to the memory
   • Control Bus
     • The control bus is bi-directional
     • Controls the flow of data between the processor and other parts of the computer.
       • This includes the synchronisation of signals and the control of access to the data and address busses

3. I/O Controllers

   • They control the flow of information and data between the processor and the input and output devices, sometimes called peripherals
   • I/O Devices: Keyboard, Monitor, Mouse etc.
     • They are connected to the computer through I/O ports like USBs
   • The data bus carries the signal between the processor to the I/O controllers and from the controllers to the devices
   • Every device has its own controller
   • Te controller translates signals from the I/O devices into the form required by the processor
   • They buffer data being sent between them because the I/O devices run at a much slower speed than the processor

4. Processor

   • Has its own Mindap

5. The stored Program Concept

   • This is the concept of storing programs and instructions electronically in machine code in main memory
   • The machine code instructions are fetched from memory, decoded and the executed in the processor. More on this in the processor section.
   • The concept was originally put forward by Von Neumann and is occupied in Von Neumann architecture
   • The concept allowed computers to be much more flexible and allowed them to do many more things
   • The concept that program instructions and data are stored together in the same memory.