UDMA
The Ultra DMA interface was the fastest method used to transfer data through the ATA controller, usually between the computer and an ATA device. UDMA succeeded Single/Multiword DMA as the interface of choice between ATA devices and the computer. There are 8 different UDMA modes, ranging from 0 to 6 for ATA, 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.
| Mode | Number | Also called | Maximum transfer
rate | Minimum cycle time | Defining standard |
| Ultra DMA | 0 | | 16.7 | 120 ns | ATA-4 |
| Ultra DMA | 1 | | 25.0 | 80 ns | ATA-4 |
| Ultra DMA | 2 | Ultra ATA/33 | 33.3 | 60 ns | ATA-4 |
| Ultra DMA | 3 | | 44.4 | 45 ns | ATA-5 |
| Ultra DMA | 4 | Ultra ATA/66 | 66.7 | 30 ns | ATA-5 |
| Ultra DMA | 5 | Ultra ATA/100 | 100 | 20 ns | ATA-6 |
| Ultra DMA | 6 | Ultra ATA/133 | 133 | 15 ns | ATA-7 |
| Ultra DMA | 7 | Ultra ATA/167 | 167 | 12 ns | CompactFlash 6.0 |
