This set of Microprocessor Multiple Choice Questions & Answers (MCQs) focuses on “Virtual 8086 Mode, the Coprocessor 80387”.
1. If the 80386 enters the protected mode from the real address mode, then it returns back to the real mode, by performing the operation of
a) read
b) write
c) terminate
d) reset
View Answer
Explanation: If the 80386 enters the protected mode from the real address mode, then it cannot return back to the real mode without a reset operation.
2. The unit that is needed for virtual mode 80386, only to run the 8086 programs, which require more than 1 Mbyte of memory for memory management functions, is
a) execution unit
b) central processing unit
c) paging unit
d) segmentation unit
View Answer
Explanation: Paging unit is not necessarily enabled in the virtual mode, but may be needed to run the 8086 programs, which require more than 1 Mbyte of memory, for memory management functions.
3. The number of pages that the paging unit allows, in the virtual mode of 80386 is
a) 64
b) 128
c) 256
d) 512
View Answer
Explanation: In virtual mode, the paging unit allows only 256 pages, each of 4Kbytes size. Each of the pages may be located anywhere within the maximum 4Gbytes physical memory.
4. The privilege level at which the real mode programs are executed is
a) level 0
b) level 1
c) level 2
d) level 3
View Answer
Explanation: The real mode programs are executed at the highest privilege level i.e. level 0.
5. The instructions to prepare the processor for protected mode can only be executed at the privilege level
a) level 0
b) level 1
c) level 2
d) level 3
View Answer
Explanation: The instructions to prepare the processor for protected mode can only be executed at the level 0.
6. The instruction that is unable to set or read the VM (Virtual Mode) bit is
a) PUSHF
b) IRET
c) POPF
d) PUSHF and POPF
View Answer
Explanation: The PUSHF and POPF instructions are unable to set or read the VM (Virtual Mode) bit, as they do not access it. The virtual mode can be entered by using IRET instruction.
7. If the CKM pin of 80387 is high, then 80387 is operated in
a) real address mode
b) protected mode
c) synchronous mode
d) asynchronous mode
View Answer
Explanation: If the CKM pin of 80387 is high, then 80387 is operated in synchronous mode. If it is low, then 80387 is operated in asynchronous mode.
8. The unit that handles the data and directs it to either FIFO or instruction decoder depending on the bus control logic directive is
a) paging unit
b) central processing unit
c) segmentation unit
d) data interface and control unit
View Answer
Explanation: The data interface and control unit handles the data, and direct it to either FIFO or instruction decoder, depending on the bus control logic directive.
9. The unit that is responsible for carrying out all the floating point calculations, allotted to the coprocessor by 80386, is
a) Central processing unit
b) ALU
c) FPU
d) None of the mentioned
View Answer
Explanation: The FPU (floating point unit) is responsible for carrying out all the floating point calculations, allotted to the coprocessor by 80386.
10. The sizes of instruction and data pointer registers of 80387 respectively are
a) 32-bit, 32-bit
b) 48-bit, 32-bit
c) 32-bit, 48-bit
d) 48-bit, 48-bit
View Answer
Explanation: 80387 consists of two 48-bit registers, known as instruction and data pointer registers.
11. To inform 80387 that the CPU wants to communicate with NPS1, the NPS1 line is directly connected to
a) A31
b) A30
c) M/IO
d) D31
View Answer
Explanation: The NPS1 and NPS2 lines are directly connected with M/IO and A31 respectively, to inform 80387 that the CPU wants to communicate with it (NPS1), and it is using one of the reserved I/O addresses for 80387 (NPS2).
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