Direct Memory Access (DMA)

Reference:

If IO device (such as disk controller) needs data to be written or read from the memory, it used to to through the CPU like below.

In the above image, if IO can talk to/access memory directly, the number of cycles will reduce drastically. To achieve this direct memory access by an IO device, a special called DMA controller is needed.

Now, there are 4 components involved in DMA theory. Picture below.

YOUTUBE LINK: https://www.youtube.com/watch?v=Xkpu8BXi3aI

Here is how it works:
1.