GATE CS 2026 Set 2 Q.18: I/O Interface, Interrupts and DMA

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

S1: In non-vectored interrupt mechanism, it usually takes more time to start the Interrupt Service Routine (ISR) when compared to that in a vectored interrupt mechanism.

S2: In 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?

Both S1 and S2 are true

Both S1 and S2 are false

S1 is true and S2 is false

S1 is false and S2 is true

Official answer and solution

Official answer: C
From: Official GATE 2026 answer key

Solution

Compare vectored vs. non-vectored interrupt latency (S1) and hardware daisy-chaining vs. software polling (S2).

S1 is true: In a vectored interrupt system, the interrupting device supplies the interrupt vector (address of the ISR) directly, whereas in a non-vectored system the CPU jumps to a fixed handler that must first identify the interrupting device before branching to its ISR.
S2 is false: In daisy-chaining, the CPU sends a single Interrupt Acknowledge (INTA) signal down a serial hardware chain; the highest-priority requesting device intercepts INTA and places its vector on the bus without the CPU polling devices individually.

Final answer

Option (C)

Common trap

Confusing hardware daisy-chaining with software polling.

The answer is the one in the official GATE answer key. The solution is this site's own explanation.

Source

Paper: GATE 2026 Computer Science and Information Technology - Session 2 (CS2)
Question: 18 of 65
Section: Computer Science and Information Technology

Report an error in this question

GATE questions are the work of the organising institutes. This site is independent and is not affiliated with them.

Question

Solution

Source