DMA Self Doubt

Question

A device has been used in DMA. A word of 4 bytes can be transferred when it is available. The memory cycle time is 40 ms and CPU is idle for 10% of its time. What is the data transfer rate of the device for Burst mode and Cycle stealing mode. 

I'm getting

Burst mode - 11.11 B/s 

Cycle stealing - 10 B/s

Is it correct??

Comments

@Ashwin Kulkarni In cycle stealing it may be 9.09 it take a time of 11 cycle to transfer 4 byte of data

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How in burst mode it's is 11.11 for 1B

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I AM ALSO GETTING THE SAME

Answer 1

Lets's suppose x = data transfer rate and y = memory cycle time

 

% time CPU idle ==  y / ( x + y ) * 100

y / ( x + y ) * 100 = 10 (given)

and y = 40 msec

 

So, 40/40+x * 100 = 10

x = 360 msec

 

So now,

360 msec -------> 4 B

1 msec ----------> 4/360 B

1 sec -------------> 11.11 Byte