GATE CSE 2024 | Set 1 | Question: 5

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 

Answer 1

Correct answer - Option C

In a system using programmed I/O, the cpu polls the devices regarding the status update of the I/O event. till the event is completed, the cpu would have wasted cycles trying to poll devices for the completion of I/O Task. In an interrupt based mechanism the CPU keeps running uninturrupted till the device activates the interrupt line indicating to the cpu about the completion of the I/O event. Hence there will not be any wasted cycles. Hence Interrupt based I/O mechanisms have better CPU utilisation rate. 

Answer 2

Option C

Because the data transfer rate in programmed I/O is slower than that of an Interrupt Driven I/O.