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Protected mode

(also protected virtual address mode)

Protected mode definition

Protected mode is an operational mode for x86-compatible central processing units (CPUs). It enables CPUs to access extended features like virtual memory, paging, and a higher range of addressable memory.

Compared to real mode, protected mode provides a more controlled and secure environment for executing programs by enforcing restrictions on how memory and hardware resources are accessed.

See also: system software, word size

History of protected mode

  • Introduction. In 1982, Intel introduced protected mode with the Intel 80286 (286) CPU.
  • Enhancements. 1985 marked the introduction of the Intel 80386 (386) — a significant advancement in protected mode operation. The 386 could address up to 4 GB of memory and introduced virtual 8086 mode, allowing older software written for the 8086 to run in a virtualized environment within protected mode.
  • Widespread adoption. Microsoft Windows and OS/2 were among the first to take full advantage of protected mode, offering better stability, security, and multitasking capabilities. It was a key factor in the transition from single-task operating systems, like MS-DOS, to the multitasking ones we use today, like Windows and Linux.
  • Modern usage. Today, protected mode is the standard operational mode for all x86 processors in modern computers. It underpins the operation of all contemporary operating systems, providing a secure and stable environment for running complex applications and managing hardware resources.