Ultra DMA [UDMA]


(n.) Ultra direct memory access; advanced implementation of DMA that allows commands to transfer data at 33.3 megabits per second (Mbps). This is twice the original Burst DMA transfer rate of 16.6 Mbps, using the same standard 40-pin Integrated Drive Electronics (IDE) interface cable. To employ UDMA, the drive and the Basic Input/Output System (BIOS) must be compatible with the new standard, and device drivers must be loaded in the operating system. UDMA allows a host computer to send and retrieve data faster, particularly during sequential operations. It provides enhanced data integrity capabilities to the EIDE interface. It does this through improved timing margins and through the use of cyclic redundancy check (CRC), a data transfer error detection code. UDMA is endorsed by most industry hard drive manufacturers, including Fujitsu, IBM, Maxtor, Quantum, Seagate, Toshiba, and Western Digital.

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