Question

The CPU nearly delays its operation for one memory cycle, to allow direct memory i/o transfer. This process is called as:
1. Cycle waiting
2. Cycle Burst
3. Cycle Stealing
4. Burst Transfer

Answer 1

Correct Answer - Option 3 : Cycle Stealing

The correct answer is Cycle Stealing.

Concept:

A technique called cycle stealing allows the DMA controller to transfer one data word at a time, after which it must return control of buses to the CPU. The CPU delays its operation only for one memory cycle to allow the direct memory I/O transfer to “steal” one memory cycle.

• Buffer the byte into the buffer
• Inform the CPU that the device has 1 byte to transfer (i.e. bus grant request)
• Transfer the byte (at system bus speed)
• Release the control of the bus back to CPU.

Therefore Correct answer is Option 3.