GATE CSE 2024 Set 1 Q15

Question

Which one of the following statements is FALSE?
A) 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
B) For bulk data transfer, the burst mode of DMA has a higher throughput than the cycle stealing mode
C) Programmed I/O mechanism has a better CPU utilization than the interrupt driven I/O mechanism
D) The CPU can start executing an interrupt service routine faster with vectored interrupts than with non-vectored interrupts

Accepted Answer

Official answer: C) Programmed I/O mechanism has a better CPU utilization than the interrupt driven I/O mechanism. Explanation: To identify the false statement, let us evaluate each option: - Option A: In cycle stealing mode of DMA, the DMA controller takes control of the system bus for one bus cycle at a time to transfer a single data word (or byte) and then releases the bus back to the CPU. This statement is TRUE. - Option B: In burst mode (block transfer mode), an entire block of data is transferred in one continuous sequence without repeatedly releasing and re-requesting the system bus. Hence, for bulk data transfer, burst mode has less arbitration overhead and achieves a higher throughput than cycle stealing mode. This statement is TRUE. - Option C: In Programmed I/O, the CPU remains in a busy-waiting (polling) loop to check the status of the I/O device until it is ready for data transfer, which severely degrades CPU utilization. In contrast, Interrupt-driven I/O frees the CPU to perform other computational tasks until the I/O device is ready and signals an interrupt, yielding much better CPU utilization. Therefore, stating that programmed I/O has better CPU utilization is FALSE. - Option D: In vectored interrupts, the interrupting device provides the interrupt vector (address or index to the vector table) directly to the CPU on the data bus, allowing the CPU to immediately branch to the corresponding Interrupt Service Routine (ISR). In non-vectored interrupts, the CPU must jump to a fixed general service routine and poll devices to find the source. Thus, ISR execution starts faster with vectored interrupts. This statement is TRUE. Hence, statement (C) is the false statement.

Answer

A) 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

Answer

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

Answer

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

Answer

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

Which one of the following statements is FALSE?

Step-by-step verified solution

Check you can still solve I/O Interface, Interrupts and DMA under a clock

More from GATE CSE 2024 Set 1

More on I/O Interface, Interrupts and DMA

Which one of the following statements is FALSE?

Step-by-step verified solution

Check you can still solve I/O Interface, Interrupts and DMA under a clock

More from GATE CSE 2024 Set 1

More on I/O Interface, Interrupts and DMA

Which one of the following statements is FALSE?

Step-by-step verified solution

Check you can still solve I/O Interface, Interrupts and DMA under a clock

More from GATE CSE 2024 Set 1

More on I/O Interface, Interrupts and DMA

Share this solution

Which one of the following statements is FALSE?

Step-by-step verified solution

Check you can still solve I/O Interface, Interrupts and DMA under a clock

More from GATE CSE 2024 Set 1

More on I/O Interface, Interrupts and DMA

Share this solution