UDMA

{{Short description|Data transfer method for ATA Hard drives}}

{{For|the main article about the interface|Parallel ATA}}

{{refimprove|date=September 2014}}

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.

File:IDE cable 40 pin & 80 pin.jpg

Modes faster than UDMA mode 2 require an 80-conductor cable to reduce data settling times, lower impedance and reduce crosstalk.[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 AT Attachment with Packet Interface - 7 Volume 2 - Parallel Transport Protocols and Physical Interconnect (ATA/ATAPI-7 V2) E.2.1.1 Cabling p172]

class="wikitable" style="text-align:center" |+Transfer Modes ! Mode	Number	Also called	Maximum transfer rate (MB/s)	Minimum cycle time	Defining standard
rowspan=8 | Ultra DMA | 0		{{0}}16.7	120 ns	ATA-4
1		{{0}}25.0	{{0}}80 ns	ATA-4
2	Ultra ATA/33{{0}}	{{0}}33.3	{{0}}60 ns	ATA-4
380-conductor cable required		{{0}}44.4	{{0}}45 ns	ATA-5
4	Ultra ATA/66{{0}}	{{0}}66.7	{{0}}30 ns	ATA-5
5	Ultra ATA/100	100{{0|.0}}	{{0}}20 ns	ATA-6
6	Ultra ATA/133	133{{0|.0}}	{{0}}15 ns	ATA-7
7	Ultra ATA/167	167{{0|.0}}	{{0}}12 ns	CompactFlash 6.0[http://compactflash.org/2010/cf-6-0-introduces-industry-leading-performance-and-feature-enhancements/ CompactFlash 6.0 Introduction] {{Webarchive|url=https://web.archive.org/web/20101121233926/http://compactflash.org/2010/cf-6-0-introduces-industry-leading-performance-and-feature-enhancements/ |date=2010-11-21 }}