Disable/enable the using_dma flag for this drive.

This option only works with a few combinations of drives and interfaces which support DMA and which are known to the IDE driver (and with all supported XT interfaces).
In particular, the Intel Triton chipset is supported for bus-mastered DMA operation with many drives (experimental).

It is also a good idea to use the Transfer Mode option in combination with to ensure that the drive itself is programmed for the best DMA mode.

Using DMA does not necessarily provide any improvement in throughput or system performance, but many folks swear by it. Your mileage may vary.