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2.2.1 Modes of Operation

  • 3 primary modes of operation
    1. Protected mode
      • Native state of processor
      • Programs are allocated segments
      • Programs are restricted from accessing memory outside its respective segment
    2. Real-address mode
      • Implements the early 8086 programming environment
      • Useful if a program requires direct access to system memory and hardware devices
    3. System management mode
      • Often used by computer manufacturers to implement low level functions such as system security or power management
    4. *Sub-mode, virtual-8086 a special version of protected mode
      • Allows the execution of very early MS-DOS programs safely, meaning no kernel panic if it crashes

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