GATE CS 2024 Set 1 Q.15: I/O Interface, Interrupts and DMA

Which one of the following statements is FALSE?

In the cycle stealing mode of DMA, one word of data is transferred between an I/O device and main memory in a stolen cycle

For bulk data transfer, the burst mode of DMA has a higher throughput than the cycle stealing mode

Programmed I/O mechanism has a better CPU utilization than the interrupt driven I/O mechanism

The CPU can start executing an interrupt service routine faster with vectored interrupts than with non-vectored interrupts

Official answer and solution

Official answer: C
From: Official GATE 2024 answer key

Solution

Compare CPU utilization under programmed I/O (busy-wait polling) versus interrupt-driven I/O.

In Programmed I/O, the CPU continuously polls the I/O device status register in a busy-wait loop until the I/O operation completes, wasting CPU cycles. In Interrupt-driven I/O, the CPU initiates the I/O request and continues executing other useful instructions until the device raises an interrupt upon completion. Therefore, programmed I/O has worse (lower) CPU utilization than interrupt-driven I/O, making statement (C) FALSE.

Final answer

Option (C)

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

Source

Paper: GATE 2024 Computer Science and Information Technology - Set 1 (CS1)
Question: 15 of 65
Section: Computer Science and Information Technology

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