Question: Explain V86 mode of 80386DX
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Mumbai University > Computer Engineering > Sem5 > Microprocessor

Marks: 5

Year: May 2016

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modified 2.7 years ago  • written 2.7 years ago by gravatar for Sagar Narkar Sagar Narkar1.5k
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  1. In protected mode of operation, 80386DX provides a virtual 8086 operating environment to execute the 8086 programs.

  2. The real mode can also use to execute the 8086 programs along with the capabilities of 80386, like protection and a few additional instructions.

  3. Once the 80386 enters the protected mode from the real mode, it cannot return back to the real mode without a reset operation.

  4. Thus, the virtual 8086 mode of operation of 80386, offers an advantage of executing 8086 programs while in protected mode.

  5. V86 Mode is also known as Virtual Mode of 80386.

  6. V86 Mode is a Dynamic Mode.

  7. It can switch repeatedly & rapidly between V86 Mode & Protected Mode.

  8. To execute an 8086 program, the CPU enters in V86 Mode from Protected Mode.

  9. CPU Leaves V86 Mode and enters protected mode to continue executing a native 80386 program.

  10. The address forming mechanism in virtual 8086 mode is exactly identical with that of 8086 real mode.

  11. In virtual mode, 8086 can address 1MB of physical memory that may be anywhere in the 4GB address space of the protected mode of 80386.

  12. Like 80386 real mode, the addresses in virtual 8086 mode lie within 1MB of memory.

  13. In virtual mode, the paging mechanism and protection capabilities are available at the service of the programmers.

  14. The virtual mode allows the multiprogramming of 8086 applications.

  15. The virtual 8086 mode executes all the programs at privilege level 3.

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written 2.7 years ago by gravatar for Sagar Narkar Sagar Narkar1.5k
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