Direct Memory Access I Ultra Direct Memory Access refers to a technology that allows a hard disk to manage data transfer with¬out the aid of the CPU. This speeds up data transfers, while also leaving the CPU to perform other tasks. DMA I UDMA have gone through many iterations, the latest being UDMA 6, which offers transfer speeds of 133 Megabytes per second.

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DMA I UDMA modes are specified in the ATA standard. To achieve speeds above 33 Megabytes per second, as envisaged in UDMA3, a spe¬cial SO-pin conductor cable is needed to reduce the interference that occurs between two data-earrying channels. Though the data is transferred using only 40 pins, the remaining pins are needed to ground interference created during the data transfer.