Selectors and Descriptor in 80286

Posted By on September 21, 2014


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Pipelining concept in 8086
Selectors and Descriptor in 80386

Selectors:used to address a 64 kB memory segment in protected model; a segment register that holds the current descriptor number; 16 bits in length

  • 2 bits for requested privilege level
  • 1 bit for table indicator (local or global)
  • 13 bits for index (8,192 possible descriptors)

Descriptors:define the use of memory space
(Global, Local, and Interrupt) – 64 bits in length

  • 24 bits for base address(start of segment)
  • 16 bits for limit (length of segment)
  • 8 bits for access bits
  • 16 bits unused (zero)

 

Types of Descriptors

  • Local Descriptor Table (LDT) Descriptor
  • Task State Segment (TSS) Descriptor
  • Gate Descriptors
    • Call Gate Descriptor
    • Task Gate Descriptor
    • Interrupt Gate Descriptor
    • Trap Gate Descriptor
Pipelining concept in 8086
Selectors and Descriptor in 80386

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Posted by Akash Kurup

Founder and C.E.O, World4Engineers Educationist and Entrepreneur by passion. Orator and blogger by hobby

Website: http://world4engineers.com