Test by Bikram | Computer Organization and Architecture | Test 1 | Question: 17

Question

The fastest mode of data transfer is:

• A. Programmable I/O
• B. Interrupt I/O
• C. DMA
• D. Both A and B

Comments

DMA is correct

Answer 1

DMA is the fastest data transfer mode , as no CPU involvement is there .

Comments

@Bikram Sir, I have a silly doubt.

Here the question says data transfer is to be done quickly.

We know that DMA initial setup takes time, and also buffer delay is counted. 

In interrupt mode, ISR execution takes time.

In programmable I/O these overheads are not counted.

For long run DMA is best, but for single immediate transfer to be perform quickly, isn't programmable I/O is the choice.

We are not talking about wastage of useful CPU time here.

Correct me if I m wrong.

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@Astitva Srivastava

 

https://www.quora.com/Why-is-DMA-an-improvement-over-CPU-programmed-I-O

 

https://www.microchip.com/forums/m1101299.aspx

 

http://cgi.cse.unsw.edu.au/~cs3231/07s1/example_exam_answers_updated.html?session=07s1

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https://gateoverflow.in/116524/coa-dma-doubt

 

https://gateoverflow.in/84276/hamacher-dma

Answer 2

Programmable I/O and Interrupt-driven I/O both require CPU to intervene, which is an overhead for data transfer.

DMA, on the other hand has Direct memory access, without the intervention of CPU. It doesn't have that overhead and hence is faster.

 

Option C