Direct Memory Access (DMA) allows devices to access memory directly rather than

Question

Direct Memory Access (DMA) allows devices to access memory directly rather than working through the CPU. This can dramatically speed up the performance of peripherals, but adds complexity to memory system implementations. Explore DMA implications by answering the questions about the following peripherals. a.Mouse Controller b.Ethernet Controller 6.11.1 [5] Does the CPU relinquish control of memory when DMA is active? For example, can a peripheral simply communicate with memory directly, avoiding the CPU completely? 6.11.2 [10] Of the peripherals listed in the table, which would benefit from DMA? What criteria determine if DMA is appropriate?

Explanation / Answer

a.

Mouse controller:

In mouse controller DMA we will control the memory access using mouse. i.e by using mouse we will decide whether we access memory directly or not. If we access up to how much extent we will access is also decided by mouse.

b.

Ethernet Controller:

In ethernet controller based dynamic memory access we will use ethernet equipment for example LAN to transfer data from one device to another device without CPU interference.

6.11.1

Yes, CPU relinquish control of memory when DMA is active.

The pheripheral will directly communicate to memory avoiding CPU interference.

A DMA channel enables a device to transfer data without exposing the CPU to a work overload. Without the DMA channels, the CPU copies every piece of data using a peripheral bus from the I/O device. Using a peripheral bus occupies the CPU during the read/write process and does not allow other work to be performed until the operation is completed.

With DMA, the CPU can process other tasks while data transfer is being performed. The transfer of data is first initiated by the CPU. During the transfer of data between the DMA channel and I/O device, the CPU performs other tasks. When the data transfer is complete, the CPU receives an interrupt request from the DMA controller.

6.11.2

Of the peripherals listed in the table, Ethernet Controller would benefit from DMA.

For mouse controller there should be other work than DMA. But for Ethernet controller is very efficient for DMA. It speeds up the data speed as compared to mouse controller.

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