Engineering Questions with Answers - Multiple Choice Questions

MCQs on Register Organisation of 80386 -1

1 - Question

The 16-bit registers are available with their extended size of 32 bits, by adding the registers with a prefix of
a) X
b) E
c) 32
d) XX

View Answer

Answer: b
Explanation: A 32 bit register, known as an extended register, is represented by the register name with a prefix of E.




2 - Question

In a 32-bit register, ESP, the lower 16-bits of the register can be represented by
a) LSP
b) FSP
c) SP
d) None of the mentioned

View Answer

Answer: c
Explanation: Though the extended size of 32 bits are named as EBP, ESP, ESI and EDI, the names BP, SP, SI and DI represent the lower 16-bits.




3 - Question

Which of the following is a data segment register of 80386?
a) ES
b) FS
c) GS
d) All of the mentioned

View Answer
Answer: d
Explanation: The six segment registers available in 80386 are CS, SS, DS, ES, FS and GS, out of which DS, ES, FS and GS are the four data segment registers.
 



4 - Question

The register width used by the 32-bit addressing modes is
a) 8 bits
b) 16 bits
c) 32 bits
d) all of the mentioned

View Answer

Answer: d
Explanation: The 32-bit addressing modes may use all the register widths, i.e. 8, 16 or 32 bits.




5 - Question

The flag that is additional in flag register of 80386, compared to that of 80286 is
a) VM flag
b) RF flag
c) VM and RF flag
d) None of the mentioned

View Answer

Answer: c
Explanation: The VM and RF flags are added to the 80286 flag register, to derive the flag register of 80386.




6 - Question

The VM (virtual mode) flag is to be set, only when 80386 is in
a) virtual mode
b) protected mode
c) either virtual or protected mode
d) all of the mentioned

View Answer

Answer: b
Explanation: If VM flag is set, the 80386 enters the virtual 8086 mode within the protected mode. This is to be set only when the 80386 is in protected mode.




7 - Question

In protected mode of 80386, the VM flag is set by using
a) IRET instruction
b) Task switch operation
c) IRET instruction or task switch operation
d) None of the mentioned

View Answer

Answer: c
Explanation: The VM flag can be set using the IRET instruction or any task switch operation, only in the protected mode.




8 - Question

During the instruction cycle of 80386, any debug fault can be ignored if
a) VM flag is set
b) VM flag is cleared
c) RF is cleared
d) RF is set

View Answer

Answer: d
Explanation: If RF (resume flag) is set, any debug fault is ignored during the instruction cycle.




9 - Question

The RF is not automatically reset after the execution of
a) IRET
b) POPA
c) IRET and POPF
d) IRET and PUSHF

View Answer

Answer: c
Explanation: The RF is automatically reset after the execution of every instruction, except for the IRET and POPF instructions. Also, it is not cleared automatically after the successful execution of JMP, CALL and INT instructions causing a task switch.




10 - Question

The segment descriptor register is used to store
a) attributes
b) limit address of segments
c) base address of segments
d) all of the mentioned

View Answer

Answer: d
Explanation: The segment descriptor register is used to store the descriptor information like attributes, limit and base addresses of segments.

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