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A certain device dumps data into its interface register every 200 ns. The main memory access time is 50 ns. If the CPU were interfaced to his device in cycle stealing mode, what percentage of time does the CPU be in hold state?
A. 20
B. 25
C. 50
D. None of these

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Answer is option B

Data Preparation time = 200 ns

Main memory access time = 50 ns = cpu is idle ( i.e in hold state )

Memory access time = Date Transfer time = 50 ns 

so the percentage of time that cpu is in hold state = ( 50/200 ) * 100 = 25 %

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