1.1 System Architecture

1.1 System Architecture

1. Processor

   • Processes Data ("Brains of the computer")
   • Carries out instructions (Executes them)
   • Clock speed measured in Hertz (Hz). This is the number of cycles per second
     • MHz (Mega Hertz)
       • 1,000,000 Hertz
     • GHz (Giga Hertz)
       • 1,000,000,000 Hertz
     • KHz (Kilo hertz)
       • 1000 Hertz
   • Cores
     • Cores allow for a processor to process multiple things at a time
       • The more cores the more instructions and data it can decode, execute and process a second. For example having 4 cores would allow you to process twice as many things than a person with a 2 core CPU.

2. Embedded systems

   • Usually has very specialised tasks
   • Doesn't contain a operating system
   • For example: A fridge, microwave, oven, alarm clock etc.

3. System Busses

   • Data Bus
     • Carries Data/instructions from the main memory to the processor
     • Bi-Directional
   • Address Bus
     • Carries addresses from the Processor to main memory or other I/O devices.
     • All data/ instructions are returned on the data bus
   • Control Bus
     • Control signals are sent along the control bus
     • This instructs which data will be travelling to/from memory

4. Secondary storage

   • Used for long term storage of data and instructions
   • EG: Hard disk drive , Solid State drive , Flash memory

5. Registers

   • MAR
     • The location of the next instruction is copied here and transferred along the Address Bus
     • Memory Address Register
   • MDR
     • Once Data/instructions are brought from the Memory Address in Main Memory - they are placed in the MDR
     • Memory Data Register
   • CIR
     • The instructions stored in the MDR are copied here
     • Current Instruction Register
   • PC- Program counter Holds the location of the next instruction/data address in Main memory

6. ALU

   • Arithmetic logic unit
   • Performs arithmetic and logical operations + , - , * , /.

7. Accumulator

   • Results of calculations are placed in here