The Ultra DMA (Ultra Direct Memory Access, UDMA) modes are the fastest methods used to transfer data through the ATA hard disk interface, usually between a computer and an ATA device. UDMA succeeded Single/Multiword DMA as the interface of choice between ATA devices and the computer. There are eight different UDMA modes, ranging from 0 to 6 for ATA (0 to 7 for CompactFlash), each with its own timing.
Modes faster than UDMA mode 2 require an 80-conductor cable to reduce data settling times, lower impedance and reduce crosstalk.AT Attachment with Packet Interface - 7 Volume 2 - Parallel Transport Protocols and Physical Interconnect (ATA/ATAPI-7 V2) E.2.1.1 Cabling p172
+ Transfer modes Mode Number Also called Maximum transferrate (MB/s) Minimumcycle time Definingstandard Ultra DMA 0 16.7 120 ns ATA-4 1 25.0 80 ns ATA-4 2 Ultra ATA/33 33.3 60 ns ATA-4 380-conductor cable required 44.4 45 ns ATA-5 4 Ultra ATA/66 66.7 30 ns ATA-5 5 Ultra ATA/100 100 20 ns ATA-6 6 Ultra ATA/133 133 15 ns ATA-7 7 167 12 ns CompactFlash 6.0CompactFlash 6.0 Introduction
See also PIO—The first interface type used between devices (mainly hard disks) and the computer. Parallel ATA Serial ATA
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