1.1 System Architechture

1.1 System Architechture

1. what is a computer system?

   • A computer system is one that is able to take a set of inputs, process them and create a set of outputs. This is done by using a combination of hardware and software.
   • An input provides data to the computer.
   • Processing involves manipulating the input data.
   • Output provides the processed data in a format that the user can understand and use.
   • The physical parts of a computer are called hardware.
   • The computer programs which provide the system with instructions are called software.
   • A bus is a set of wires which carry data around the computer system.
   • An embedded computer system is one that is part of a larger piece of equipment such as a television and has a specific task to carry out.

2. The Purpose and Components of a CPU

   • The purpose of a CPU is to process data and control other components within the computer system.
   • The CPU is located on a 'motherboard'.
   • The three main parts of a CPU are the Control Unit, Registers and the Arithmetic Logic Unit (ALU).
   • The three main buses are Data bus, Address bus and the Control bus. These connect parts of the computer system.
   • The cache is a very fast but small type of RAM.
   • The CPU runs at the speed of its clock.

3. Von Neumann architecture

   • Another name for the Von Neumann architecture is the stored program computer
   • A computer architecture is not an actual computer but the idea of how a computer could be built.
   • The Von Neumann architecture includes program and data loaded into memory
   • Registers in a CPU includes the Memory Data Register (MDR) and the Memory Address Register (MAR)
   • The Program Counter contains the the address of the next instruction
   • The Accumulator holds temporary data whilst processing is underway.
   • Modern CPUs include a number of extra general purpose registers to make programs more efficient than having a single register needing to contain every temporary data item.

4. Fetch- Decode-Execute

   • Software or program is initially loaded into main memory (RAM)
   • A process called the Fetch-Decode-Execute cycle handles each instruction one at a time.
   • The cycle also handles the loading of data from memory
   • The first stage is 'Fetch' which loads an instruction or data from memory into the CPU
   • The second stage is 'Decode'. The instruction is decoded by the Control Unit so the CPU can handle the last stage
   • The third stage is 'Execute' which means carry out the instruction