UDMA

The Ultra DMA (Ultra Direct Memory Access, UDMA) 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 (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]

Transfer Modes
ModeNumberAlso calledMaximum transfer
rate (MB/s)
Minimum cycle timeDefining 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

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