direct memory access

Direct memory access (DMA) is a feature of many computer systems that allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU).

Without DMA, programmed input–output must be used to transfer data which typically fully occupies the CPU for the entire duration of the transfer, and is thus unavailable to perform other work. With DMA, the CPU first initiates the transfer, then it does other operations while the transfer is in progress, and it finally receives an interrupt from the direct memory access controller (DMAC) when the operation is done. This feature is useful at any time that the CPU cannot keep up with the rate of data transfer, or when the CPU needs to perform work while waiting for a relatively slow data transfer.