Computer System

Computer System

1. Architecture of CPU

   • Purpose of CPU
     • Processes all data and instructions, power depends on other characteristics.
   • Fetch and Decode Cycle
     • Fetches, decodes then executes instructions
   • Arithmetic Logic Unit (ALU)
     • performs calculations and logical comparisons
   • Control Unit (CU)
     • sends signals to control data around CPU
   • Cache
     • memory on CPU providing fast access to frequently used data and instructions
   • Registers
     • Program Counter (PC)
       • holds address of the next instruction
     • Memory Address Register (MAR)
       • holds address of data ready for MDR, or address of instruction passed by PC
     • Memory Data Register (MDR)
       • holds data fetched from or to be written to the memory
     • Accumulator (ACC)
       • holds result of calculations

2. Central Processing Unit Performance

   • Clock Speed
     • Number of instructions a single processor can carry out in a second measures in Hz (Hertz), on average a desktop computer can do 3.5 GHz
     • Higher the clock speed, the greater amount of instructions that can be carried out
     • Some CPU's can be overclocked but this can lead to overheating and crashing so usually need cooling
   • Cache Size
     • Data storage inside the CPU that is much faster than RAM
     • A larger CPU cache gives the CPU faster access to more data it needs to process
   • Number of Cores
     • Each core in the CPU cab process data independently
     • The more cores a CPU has the more instructions it can carry out at once
     • Most PCs and smartphones have 4 or more cores

3. Embedded Systems

   • Purpose and Characteristics
     • A computer system built into another device usually dedicated to a singular task
     • Within a larger mechanical or electrical sytem designed for a specalist system
   • Examples
     • A car -- control fuel efficiency
     • Washing Machine -- run algorithim to wash clothes
     • Airplane -- auto-pilot