DMA Transfer rate

Question

Consider 8-bit DMA device operating in cycle stealing mode (Single Transfer Mode). Each DMA cycle takes 6 clock and each clock is of 2 MHz. An intermediate CPU machine cycle take 2 μsec. What is the data transfer rate of DMA?

Ans. 200 KB/sec

Comments

Here clock rate is 2MHz so 0.5µ secs.

Now as we are using cycle stealing mode... so to transfer 8-bits or 1 byte, DMA takes 6*0.5= 3µ sec.

And as it has to take bus from CPU so it takes 2µ sec.

So we can say, to transfer 1 byte it takes 5µ sec.

So we can say transfer rate is 200KB/sec.

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I don't understand why u are including the intermediate  CPU time for data transfer

Answer 1

Here clock rate is 2MHz so 0.5µ secs.

Now as we are using cycle stealing mode... so to transfer 8-bits or 1 byte, DMA takes 6*0.5= 3µ sec.

And as it has to take bus from CPU so it takes 2µ sec.

So we can say, to transfer 1 byte it takes 5µ sec.

So we can say transfer rate is 200KB/sec.