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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 Details By Number ]

DMA1

Channel Number: 1

Bus Line: 8/16-bit

Typical Default Use: Low DMA channel for sound card.

Other Common Uses: SCSI host adapters, ECP parallel ports, tape accelerator cards, network cards, voice modems.

Description: This DMA channel is normally taken by the sound card in your PC for its "low" DMA channel. Most sound cards today actually use two DMA channels; one must be chosen from DMAs 1, 2 or 3, while the other can be any free DMA channel (and so is selected from the less-used 5, 6 or 7). DMA1 is also a popular choice for many other peripherals, largely for historical reasons (on the original XT, DMA3 was used for the hard disk so DMA1 was all that was left open for everything else to share).

Conflicts: DMA1 is one of the two most contested channels in the system (the other being DMA3, which is often worse). It is important to watch for conflicts between multiple devices here, particularly if you are using a sound card. It is preferable in general to leave the sound card on DMA1 and move any other devices out of its way, for compatibility with older (poorly written) software that assumes the sound card is on DMA1. Also watch out for ECP parallel port conflicts here. More general solutions to resource conflicts can be found in the conflict resolution area of the Troubleshooting Expert.

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