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GATE 2026 CS (CS2) – Question 18

Computer Organization and Architecture · I/O Interface: Interrupt and DMA · 1 mark · Multiple choice

Consider the following two statements about interrupt handling mechanisms in a CPU.

$S1$: In a non-vectored interrupt mechanism, it usually takes more time to start the Interrupt Service Routine (ISR) than in a vectored interrupt mechanism.
$S2$: In a daisy-chain interrupt mechanism, the CPU polls all the input devices individually to determine the source of the interrupt.

Which one of the following options is correct with respect to $S1$ and $S2$?

  1. Both $S1$ and $S2$ are true
  2. Both $S1$ and $S2$ are false
  3. $S1$ is true and $S2$ is false
  4. $S1$ is false and $S2$ is true

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Correct answer: (C) $S1$ is true and $S2$ is false

Explanation

Statement $S1$ is true because in a non-vectored interrupt system, extra steps are required to identify the interrupt source before the ISR can begin. Statement $S2$ is false because in a daisy-chain mechanism the interrupt acknowledge signal propagates through the devices; the CPU does not individually poll each device. Therefore, option (C) is correct.