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General Information - 

UDMA ( Ultra Direct Memory Access )

UltraATA also known as UltraDMA and Bus Mastering -

A technology used by hard drives. UDMA/66 is backward compatible to the DMA format. 

It needs a compatible chipset on your system motherboard or an Ultra ATA/33, ATA/66, or an ATA/100 adapter to operate. The BIOS must also support these modes. The motherboard and the hard drive controller must support UDMA and the hard drive has to be UDMA compliant.

The faster timing requirements of Ultra ATA/66 and ATA/100 require the use of a special 80-conductor cable. This cable is color coded so that the motherboard connector is colored blue and has a black connector for the primary drive (connected to the end of the cable), and a gray connector for the secondary drive.

These cables are fully backward compatible with standard/legacy ATA drives. However, these cables will typically utilize the cable select (CS) configuration on ATA drives for defining a master or slave device (drive 0 or drive 1). In this configuration, the Master Drive (drive 0) is the connector located on the end of the cable on the opposite side of the blue connector and the Slave (drive 1) is the second connector from the end (the inside connector).

Ultra ATA cables are also limited to a maximum cable length of 18 inches. 

If you have a newer motherboard, it most likely will have 2 black IDE connectors and 2 white connectors. The black connectors are for older IDE drives and the white connectors are only for UDMA/66 drives using the special cable.

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