Microprocessors Questions and Answers – Numeric Processor 8087 -1

This set of Microprocessor Multiple Choice Questions & Answers (MCQs) focuses on “Numeric Processor 8087 -1”.

1. The unit that executes all the numeric processor instructions in 8087 is
a) Control unit
b) ALU
c) Numeric extension unit
d) None of the mentioned
View Answer

Answer: c
Explanation: The 8087 is divided into two sections namely control unit and numeric extension unit in which the numeric extension unit executes all the numeric processor instructions.

2. The unit that receives and decodes the instructions in 8087 is
a) Control unit
b) ALU
c) Numeric extension unit
d) None of the mentioned
View Answer

Answer: a
Explanation: The control unit receives, decodes the instructions, and executes the 8087 control instructions.

3. The control unit functions in
a) establishing communication between CPU and memory
b) coordinating the internal coprocessor execution
c) reads and writes memory operands
d) all of the mentioned
View Answer

Answer: d
Explanation: The control unit is used for establishing communication between CPU and memory and coordinating the internal coprocessor execution.
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4. When the numeric extension unit (NEU) begins its execution, then the signal that is active is
a) BUSY (active high)
b) BUSY (active low)
c) READY (active low)
d) RESET (active high)
View Answer

Answer: a
Explanation: When NEU begins its execution, the BUSY signal is pulled up. Also, this output signal when high, indicates to the CPU that it is busy with the execution of an allotted instruction.

5. The register that allows the register programmer to select the required processing options is
a) significant
b) exponent
c) control word register
d) none of the mentioned
View Answer

Answer: c
Explanation: The control word register allows the register programmer to select the required processing options out of available ones. It is used to control the operation of 8087.
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6. Invalid operation is the exception generated due to
a) stack overflow
b) stack underflow
c) indeterminate form as result
d) all of the mentioned
View Answer

Answer: d
Explanation: Invalid operation is generated due to stack overflow, stack underflow, indeterminate form as result, or non-number (NAN) as operand.

7. The exception generated for a too big result to fit in the format is
a) invalid operation
b) overflow
c) denormalized operand
d) result overflow
View Answer

Answer: b
Explanation: A too big result to fit in the format generates this exception. The condition code bits indicate that the result is prohibitively large.
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8. If the result is infinity, then the exception generated is
a) overflow
b) invalid operation
c) denormalized operand
d) zero divide
View Answer

Answer: d
Explanation: If any non-zero finite operand is divided by zero, the zero divide exception is generated. The resulting condition code bits indicate that the result is infinity, even if the exception is masked.

9. To operate 8087 in maximum mode, the pin MN/MX (active low) is
a) connected to Vcc or power supply
b) connected to ground
c) left unconnected
d) none of the mentioned
View Answer

Answer: b
Explanation: The 8087 can operate in a maximum mode, only when the MN/MX (active low) pin of the CPU is grounded. In maximum mode, all the control signals are derived using a sequence chip known as a bus controller.
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10. If the result is rounded according to the rounding control bits, then the exception generated is
a) denormalized operand
b) underflow
c) inexact result
d) invalid operation
View Answer

Answer: c
Explanation: If it is impossible to fit the actual result in the specified format, the result is rounded according to the rounding control bits, and an exception is generated. This sets the precision exception flag.

11. The instruction that stores a copy of top of the stack into the memory, and pops the top of the stack is
a) FST
b) FSTP
c) FIST
d) FLD
View Answer

Answer: b
Explanation: FSTP (store floating point number and pop) stores a copy of top of the stack into memory or any coprocessor register, and then pops the top of the stack.

12. The instruction that multiplies the content of the stack top by 2n is
a) FMUL
b) FPREM
c) FSCAL
d) FCSH
View Answer

Answer: c
Explanation: FSCAL instruction multiplies the content of the stack top by 2n, where n is an integral part of stack and stores the result in stack.

13. If the opcode bit is D=1, then the source and destination operands are
a) incremented
b) decremented
c) cleared
d) interchanged
View Answer

Answer: d
Explanation: If D=1, then it interchanges the source and destination operands.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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