GATE 2016 CS – Question 41
The size of the data count register of a DMA controller is 16 bits. The processor needs to transfer a file of 29,154 kilobytes from disk to main memory. The memory is byte addressable. The minimum number of times the DMA controller needs to get the control of the system bus from the processor to transfer the file from the disk to main memory is ________.
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Correct answer: 456
Explanation
A 16-bit count register lets the controller move at most $2^{16} = 65536$ bytes, which is 64 KB, each time it takes the bus. The file has $29154$ KB, so it needs $\frac{29154}{64} = 455.5$ transfers, which rounds up to 456.