Computer System Internal components - The processor - Main memory - I / O controllers - Buses External components (peripherals). These include: - keyboard - mouse - printer - disk drives

Three Box Model (von Neumann architecture)

Processor and Memory Processor executes programs and supervises functioning of the rest of the system Use Google to find out what Moore’s law is and put into your notes Memory – use e.g. in Google : define RAM to find out what it is RAM ROM EEPROM

Buses Bus: A set of parallel wires connecting 2 or more components of the computer

System Buses ADDRESS BUS – carries address from CPU to memory DATA BUS – carries data to CPU from memory CONTROL BUS – for control signals These connect the processor, memory and I/O controllers.

Control Bus Signals travel in both directions Only 1 component can use a bus at a time so the Control bus transmits command, timing and status information between components to prevent conflict.

Data Bus Signals travel in both directions Typically consists of 6, 16, 32 or 64 separate lines for moving data and instructions between components The width of the data bus is helps determine overall system performance

Address Bus Addresses travel one-way – to memory or to an I/O controller The width determines the maximum possible memory capacity of the system 1 line allows 2 1 maximum addressable cells 8 lines allows 2 8 maximum addressable cells lines allows 2 20 maximum addressable cells –

Components of a simple computer system Long term storage of programs & data

I/O Controllers The processor controls and communicates with a peripheral device through an I/O controller. Some controllers operate both input & output of bits eg. Floppy disk controller Some controllers operate in one direction only eg. VDU controller - output Keyboard input controller - input

I/O Controllers The controller is an electronic circuit board consisting of 3 parts An interface to connect to the system or I/O bus A set of registers An interface to connect to the device’s cable