1.1 System Architecture

1.1 System Architecture

1. PROCESSOR

   • brains of the computer system
   • clock speed
     • executes/carries out instructions
     • measured in hertz
     • number of cycles per second
     • MHz-GHz
       • e.g. 1GHz = executes 1 billion instructions per second
   • cores
     • each processor has a core
     • they can be multi core,dual core, quad core, 8 core
     • quadrupling the number of cores may quadruple the number of instructions
     • allows more programs to run at the same time (more cores)
   • cache
     • very fast
     • small amount of memory on processor chip
     • acts as intermediary between processor and main memory
     • holds commonly used instructions
     • bigger cache=more space to hold frequently used instructions
   • retrieves data from main memory
   • PC
     • holds location of the next instruction in main memory

2. EMBEDDED SYSTEM

   • hardware+software
     • often known as firmware
   • a computer system that is built into another device
   • to tell a machine its specific, predefined job

3. MAIN MEMORY

   • RAM
     • holds data/instructions currently in use by the processor
     • Random Access Memory
     • volatile
   • located on motherboard
   • ROM
     • Read Only Memory
     • instructions permanently etched onto chip
     • non volatile
     • bootstrap loader is held in ROM
       • gives instructions to start up the operating system
   • EEPROM
     • Electronically Erasable Programmable Read Only Memory
     • e.g. sim cards/flash memory
     • data can be removed electronically and be replaced

4. SYSTEM BUSSES

   • set of parallel wires two or more independent components
     • to pass signals
   • split into three buses
     • data bus
       • instructions returned on data bus
       • carries instructions from main memory to processor/secondary storage
       • bi-directional (two way)
       • data can be read/written
     • address bus
       • carries addresses from processor to main memory
       • one direction (uni-directional)
       • processor generates address
     • control bus
       • control signals sent along control bus
       • instructs data to/from memory

5. CPU

   • Control Processing Unit
   • Peripherals
     • devices that are not directly connected to CPU
     • e.g. mouse, keyboard, printer
     • known as I/O devices (input/output devices)
       • I/O ports
         • allow communication from I/O device and motherboard
   • Secondary Storage
     • used for long term storage of data
     • e.g. hard disk drive, DVD-R
   • fetch, decode and execute instructions