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For the main article about the interface, see 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 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

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

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]

References

↑ AT Attachment with Packet Interface - 7 Volume 2 - Parallel Transport Protocols and Physical Interconnect (ATA/ATAPI-7 V2) E.2.1.1 Cabling p172
1 2 3 4 80-conductor cable required
↑ CompactFlash 6.0 Introduction Archived 2010-11-21 at the Wayback Machine

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