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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.[1]
| Mode | Number | Also called | Maximum transfer rate (MB/s) | Minimum cycle time | Defining standard |
|---|---|---|---|---|---|
| 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 | |
| 3[2] | 44.4 | 45 ns | ATA-5 | ||
| 4[2] | Ultra ATA/66 | 66.7 | 30 ns | ATA-5 | |
| 5[2] | Ultra ATA/100 | 100 | 20 ns | ATA-6 | |
| 6[2] | Ultra ATA/133 | 133 | 15 ns | ATA-7 | |
| 7 | Ultra ATA/167 | 167 | 12 ns | CompactFlash 6.0[3] |
See also
edit- PIO—The first interface type used between devices (mainly hard disks) and the computer.
- Parallel ATA
- Serial ATA
References
edit- ↑ AT Attachment with Packet Interface - 7 Volume 2 - Parallel Transport Protocols and Physical Interconnect (ATA/ATAPI-7 V2) E.2.1.1 Cabling p172
- 1 2 3 4 80-conductor cable required
- ↑ CompactFlash 6.0 Introduction Archived 2010-11-21 at the Wayback Machine