Intel 253668-032US 사용자 설명서

17-26   Vol. 3

8086 EMULATION

Table 17-2.  Software Interrupt Handling Methods While in Virtual-8086 Mode

Method VME IOPL

Bit in 

Redir. 

Bitmap*

Processor Action

1

0

3

X

Interrupt directed to a protected-mode interrupt handler:
• Switches to privilege-level 0 stack

• Pushes GS, FS, DS and ES onto privilege-level 0 stack

• Pushes SS, ESP, EFLAGS, CS and EIP of interrupted task onto 

privilege-level 0 stack

• Clears VM, RF, NT, and TF flags

• If serviced through interrupt gate, clears IF flag

• Clears GS, FS, DS and ES to 0

• Sets CS and EIP from interrupt gate

2

0

 < 3

X

Interrupt directed to protected-mode general-protection 

exception (#GP) handler.

3

1

< 3

1

Interrupt directed to a protected-mode general-protection 

exception (#GP) handler; VIF and VIP flag support for handling 

class 2 maskable hardware interrupts.

4

1

3

1

Interrupt directed to protected-mode interrupt handler: (see 

method 1 processor action).

5

1

3

0

Interrupt redirected to 8086 program interrupt handler:
• Pushes EFLAGS 

• Pushes CS and EIP (lower 16 bits only)

• Clears IF flag

• Clears TF flag

• Loads CS and EIP (lower 16 bits only) from selected entry in 

the interrupt vector table of the current virtual-8086 task

6

1

< 3

0

Interrupt redirected to 8086 program interrupt handler; VIF and 

VIP flag support for handling class 2 maskable hardware 

interrupts:
• Pushes EFLAGS with IOPL set to 3 and VIF copied to IF

• Pushes CS and EIP (lower 16 bits only)

• Clears the VIF flag

• Clears TF flag

• Loads CS and EIP (lower 16 bits only) from selected entry in 

the interrupt vector table of the current virtual-8086 task

NOTE:

* When set to 0, software interrupt is redirected back to the 8086 program interrupt handler; 

when set to 1, interrupt is directed to protected-mode handler.