What is the main benefit of direct memory access (DMA)?
Correct answer A. A device controller moves whole blocks of data to or from memory without the CPU handling each byte
Explanation
With DMA the CPU sets up the transfer by giving the controller a memory address, a count and a direction, then carries on with other work. The DMA controller moves the data and raises a single interrupt when the whole block is done. Programmed I/O would make the CPU move each byte or word itself, which wastes cycles for fast block devices such as disks.
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