Some of Compaq�s new Presarios contain Ultra DMA enabled drives. Ultra DMA is a protocol for the ATA/IDE hard disk drive interface that doubles the current burst data transfer rate to 33 megabytes (MB) per second.

The protocol is implemented in industry standard hard drive products and enabled through logic in all new Intel PCI sets and AGP sets beginning with the 440LX.

Ultra DMA "widens" the path to the hard drive by transferring twice as much data per clock cycle. The net effect is that the maximum burst data transfer rate from the disk drive increases from 16.6 megabytes per second (MB/s) to 33 MB/s. Hard disk drive manufacturers can now bring higher performance products to market that will scale with the rest of the PC platform (faster hard drives to feed faster processors, memory and graphics).

The Ultra DMA protocol lets host computers (PCs) send and retrieve data faster, removing bottlenecks associated with data transfers -- especially during sequential operations. Users of new PCs will need less time to boot their systems and open applications, a direct result of the improved throughput provided by Ultra DMA. Current disk drive technology has been optimized to perform within the limits of the legacy protocol (16.6MB/s). Raising the data transfer headroom results in moderate performance gains with today�s drive technology. Even greater performance improvements will emerge as drive manufacturers introduce products that generate a faster data stream.

Bus Mastering technology can also be implemented with Ultra DMA disk drives. Similar reductions in CPU utilization will be experienced when Bus Mastering drivers are installed.

In addition to speed improvements, the protocol brings new data integrity capabilities to the ATA/IDE interface. Improved timing margins and the use of Cyclical Redundancy Check (CRC), a data protection verification not implemented in legacy ATA modes, help ensure the integrity of transferred data.