Direct memory access

Direct memory access (DMA) lets a hardware device transfer data to or from main memory without the processor handling each transfer. The processor typically configures the transfer and is notified when it finishes.

DMA controller: A hardware unit that coordinates DMA transfers between devices and memory. It executes transfer requests that the processor has configured.
Computer memory: Hardware that stores data and instructions for a computer system. DMA transfers data to or from this storage, usually main memory.
Disk controller: Hardware that manages data transfers between storage devices and a computer. Disk controllers use DMA to move blocks between drives and memory.
Programmed input/output: A data-transfer method in which the processor repeatedly reads or writes device data. Unlike DMA, it requires processor involvement for each data movement.
Bus mastering: A device's ability to initiate data transfers across a computer bus. A bus-mastering device can take control of the bus to perform DMA.
System bus: A communication pathway connecting processors, memory, and other computer components. DMA transfers use shared or dedicated interconnects to reach memory.
Network interface controller: A device that connects a computer to a data network. Network cards use DMA to place received packets in memory and fetch outgoing ones.
Interrupt-driven I/O: An I/O method in which a device interrupts the processor when it needs service. It reduces polling but still makes the processor handle data transfers.
Interrupt: A signal that prompts a processor to handle an event requiring attention. Devices commonly interrupt the processor when a DMA transfer completes.
Physical address: An address identifying a location in physical memory. DMA devices generally need usable physical memory addresses for transfer buffers.

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