Acronym for Ultra Direct Memory Access. This is a protocol originally developed jointly by Quantum and Intel for transferring data between a computer's hard disk and its memory. The maximum data burst rate of an Ultra DMA hard drive is 33.3 mbps. The original DMA protocol served the same purpose as UDMA, but could only transfer data at about half the speed. Utilizing UDMA, programs can open faster and run more smoothly. This is because UDMA can send more data to the memory in less time than hard drives that don't support UDMA. Also, UDMA has a built in utility called Cyclical Redundancy Checking (CRC) which helps protect data better than earlier protocols.