DMA is a technique for moving data from the computer's Memory to another component without having the Processor analyze it first. While the Processor processes the majority of the data your computer inputs or outputs, some data doesn't need to be processed or can be handled by a different device. DMA is a quicker and more effective method to transfer data from the computer's RAM to external devices in these circumstances.

For instance, a sound device might require access to data kept in the computer's Memory, but since it has the ability to handle the data, it might use DMA to avoid the CPU. DMA-capable video devices can also reach system memory and handle images without a Microprocessor. Compared to older hard drives that needed the data to be processed by the Processor first, ultra DMA hard drives use DMA to transmit data more quickly.

Devices must be allocated to a DMA channel in order to use direct memory access. Every attached device can be given a different collection of DMA channels by the interface type on a computer. A hard disk driver and a PCI controller, for instance, both have their own collection of DMA channels.