UDMA
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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.
| Mode | Number | Also called | Maximum transfer rate (MB/s) | Minimum cycle time | Defining standard |
|---|---|---|---|---|---|
| Ultra DMA | 0 | 016.7 | 120 ns | ATA-4 | |
| 1 | 025.0 | 080 ns | ATA-4 | ||
| 2 | Ultra ATA/330 | 033.3 | 060 ns | ATA-4 | |
| 3 | 044.4 | 045 ns | ATA-5 | ||
| 4 | Ultra ATA/660 | 066.7 | 030 ns | ATA-5 | |
| 5 | Ultra ATA/100 | 100.0 | 020 ns | ATA-6 | |
| 6 | Ultra ATA/133 | 133.0 | 015 ns | ATA-7 | |
| 7 | Ultra ATA/167 | 167.0 | 012 ns | CompactFlash 6.0 |
See also
- PIO—The first interface type used between devices (mainly hard disks) and the computer.
- Parallel ATA
- Serial ATA