The Ultra DMA (Ultra Direct Memory Access, UDMA) modes were the fastest method used to transfer data through the ATA hard disk interface, 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 eight different UDMA modes, ranging from 0 to 6 for ATA (0 to 7 for CompactFlash), each with its own timing.

80-conductor cable used for modes faster than UDMA 2 on the left compared to a 40-conductor cable

Modes faster than UDMA mode 2 require an 80-conductor cable to reduce data settling times, lower impedance and reduce crosstalk.[1]

Transfer Modes
ModeNumberAlso calledMaximum transfer
rate (MB/s)
Minimum
cycle time
Defining
standard
Ultra DMA 016.7120 nsATA-4
125.080 nsATA-4
2Ultra ATA/3333.360 nsATA-4
3[2]44.445 nsATA-5
4[2]Ultra ATA/6666.730 nsATA-5
5[2]Ultra ATA/10010020 nsATA-6
6[2]Ultra ATA/13313315 nsATA-7
7Ultra ATA/16716712 nsCompactFlash 6.0[3]

See also

References

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