[ Show your work/calculation in detail ] A DMA module is transferring characters

Question

[Show your work/calculation in detail] A DMA module is transferring characters (each encoded using a byte) to main memory from an external device transmitting at 12,000 bits per second (bps). The processor can fetch instructions (each instruction is encoded using a byte) at the rate of 1 million instructions per second. By how much (in percentage value) will the processor be slowed down due to the DMA activity? Explain (or, show your work). [Hint: you may ignore actual data read/write and assume that the processor only fetches instructions.]   

Explanation / Answer

The acronym DMA stands for direct memory access. In this method, the I/O processor, called a DMA device, handles the entire input or output process without help from the CPU. All that the CPU has to do is initialize the DMA device by means of a few instructions, following which the DMA device starts, and it performs the entire input or output operation independently of the CPU. After initializing the DMA device, the CPU continues its fetch-execute cycle and executes the program without having to worry about the details of the I/O. This makes DMA suitable for large quantities of I/O, and also makes it fast. In fact, using DMA is like having two processes running simultaneously in the computer. One is the processor, executing programs, and the other is the DMA device, controlling the I/O process. The DMA device causes data to be moved between the I/O device and memory directly. The word

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