Which one of the following statements is FALSE?

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.