1.1 System Architecture Updated

1.1 System Architecture Updated

1. System Buses

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

2. Registers

   • A small set of data storage place that is found in the CPU
   • PC- Program counter Holds the location of the next instruction/data address in Main memory
   • (MDR) Memory Data Register
     • MDR holds data that has been fetched or is about to be sent to memory
   • (CIR) Current Instruction Register
     • The instructions stored in the MDR are copied here
   • (MAR) Memory Address Register
     • The location of the next instruction is copied here and transferred along the Address Bus

3. Secondary Storage

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

4. Control unit

   • Decodes instructions
   • Sends Control signals

5. Arithmetic logic unit (ALU)

   • Performs arithmetic and logical operations +, - ,*,/

6. Accumulator

   • Results of calculations are placed in here

7. Processor

   • CPU
     • Decodes, fetches and executes instructions
       • Fetch Decode Execute cycle
   • Processes Data ("Brains of the computer")
   • Clock speed measured in Hertz (Hz). This is the number of cycles per second
     • KHz (Kilo Hertz)
       • 1000 Hertz
     • GHz (Giga Hertz)
       • 1,000,000,000 Hertz
     • MHz (Mega Hertz)
       • 1,000,000 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.

8. Embedded systems

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

9. Von neuman architecture

   • Jon Von Neuman created first design that had stored programs
     • VN architecture fetches instructions from memory and executes them
       • Programs were made up of sequences of instructions stored in the main memory outside CPU, fetched 1 by 1 to the registers for processing

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