# UDMA

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Data transfer method for ATA hard drives

For the main article about the interface, see [Parallel ATA](/source/Parallel_ATA).

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The **Ultra DMA** (**Ultra Direct Memory Access**, **UDMA**) modes are the fastest methods used to transfer data through the [ATA](/source/Parallel_ATA) [hard disk](/source/Hard_disk) [interface](/source/Interface_(computing)), usually between a computer and an ATA device. UDMA succeeded [Single](/source/Single_word_DMA)/[Multiword DMA](/source/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](/source/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](/source/Settling_time), lower [impedance](/source/Electrical_impedance) and reduce [crosstalk](/source/Crosstalk).[1]

[SanDisk](/source/SanDisk) 32 GB [CF](/source/CompactFlash) card supporting [VPG20](/source/CompactFlash#Video_Performance_Guarantee) and UDMA7

Transfer modes 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[2] 044.4 045 ns ATA-5 4[2] Ultra ATA/660 066.7 030 ns ATA-5 5[2] Ultra ATA/100 100.0 020 ns ATA-6 6[2] Ultra ATA/133 133.0 015 ns ATA-7 7 Ultra ATA/167 167.0 012 ns CompactFlash 6.0[3]

## See also

- [PIO](/source/Programmed_input%2Foutput)—The first interface type used between devices (mainly hard disks) and the computer.

- [Parallel ATA](/source/Parallel_ATA)

- [Serial ATA](/source/Serial_ATA)

## References

1. **[^](#cite_ref-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](https://archive.org/stream/SCSISpecificationDocumentsATAATAPI/ATA_ATAPI/AT%20Attachment%20with%20Packet%20Interface%20-%207%20Volume%202%20-%20Parallel%20Transport%20Protocols%20and%20Physical%20Interconnect%20%28ATA_ATAPI-7%20V2%29%20Revision%204b#page/n189/mode/2up)

1. ^ [***a***](#cite_ref-80c_2-0) [***b***](#cite_ref-80c_2-1) [***c***](#cite_ref-80c_2-2) [***d***](#cite_ref-80c_2-3) 80-conductor cable required

1. **[^](#cite_ref-3)** [CompactFlash 6.0 Introduction](http://compactflash.org/2010/cf-6-0-introduces-industry-leading-performance-and-feature-enhancements/) [Archived](https://web.archive.org/web/20101121233926/http://compactflash.org/2010/cf-6-0-introduces-industry-leading-performance-and-feature-enhancements/) 2010-11-21 at the [Wayback Machine](/source/Wayback_Machine)

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