What is DMA?
DMA stands for Direct Memory Access, a capability in modern computers that allows peripheral devices to send data to the motherboard’s memory without intervention from the CPU. The DMA controllers are special hardware – now embedded into the chip in modern integrated processors – that manage the data transfers and arbitrate access to the system bus. The controllers are programmed with source and destination pointers (where to read/write the data), counters to track the number of transferred bytes, and settings, which includes I/O and memory types, interrupts and states for the CPU cycles. Transfers are initiated when the DMA controller is notified of the need to move data to the memory by some event (keyboard press or mouse click, for examples). The controller asserts a DMA request signal to the CPU to use the system bus. The CPU completes its current operation and yields control of the bus to the DMA controller via a DMA acknowledge signal. The controller then reads and writes data an
