Article · Wikipedia archive · Last revised May 31, 2026

UDMA

The Ultra DMA 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, each with its own timing.

Last revised
May 31, 2026
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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.

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

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

SanDisk 32 GB CF card supporting VPG20 and UDMA7 source ↗
Transfer modes
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
32 44.4 45 ns ATA-5
42 Ultra ATA/66 66.7 30 ns ATA-5
52 Ultra ATA/100 100 20 ns ATA-6
62 Ultra ATA/133 133 15 ns ATA-7
7 Ultra ATA/167 167 12 ns CompactFlash 6.03
See also

See also

References

References

  1. AT Attachment with Packet Interface - 7 Volume 2 - Parallel Transport Protocols and Physical Interconnect (ATA/ATAPI-7 V2) E.2.1.1 Cabling p172
  2. 80-conductor cable required
  3. CompactFlash 6.0 Introduction Archived 2010-11-21 at the Wayback Machine