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[ The PC Guide | Systems and Components Reference Guide | Motherboard and System Devices | System Resources | Direct Memory Access (DMA) Channels | DMA Channel Function and Operation ]

Third-Party and First-Party DMA (Bus Mastering)

Standard DMA is sometimes called "third party" DMA. This refers to the fact that the system DMA controller is actually doing the transfer (the first two parties are the sender and receiver of the transfer). There is also a type of DMA called "first party" DMA. In this situation, the peripheral doing the transfer actually takes control of the system bus to perform the transfer. This is also called bus mastering.

Bus mastering provides much better performance than regular DMA because modern devices have much smarter and faster DMA circuitry built into them than exists in the old standard ISA DMA controller. Newer DMA modes are now available, such as Ultra DMA (mode 3 or DMA-33) that provide for very high transfer rates.

Next: Limitations of Standard DMA


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