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GATE 2013 CS (CS1) – Question 38

Computer Organization and Architecture · Instruction Set and Addressing Modes · 2 marks · Multiple choice

Micro-operations are MBR←PC; MAR←X; PC←Y; Memory←MBR. Which operation can they implement?

  1. Instruction fetch
  2. Operand fetch
  3. Conditional branch
  4. Initiation of interrupt service

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Correct answer: (D) Initiation of interrupt service

Explanation

The old program counter is saved via MBR to the memory address X while PC is replaced by service-entry address Y. Saving the return address and transferring control to a handler is interrupt-service initiation, D. An ordinary fetch does not save the old PC to memory this way.

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