UDMA

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

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.<ref>AT Attachment with Packet Interface - 7 Volume 2 - Parallel Transport Protocols and Physical Interconnect (ATA/ATAPI-7 V2) E.2.1.1 Cabling p172</ref>

Transfer modes

Mode	Number	Also called	Maximum transfer rate (MB/s)	Minimum cycle time	Defining standard
Ultra DMA	0		Template:016.7	120 ns	ATA-4
	1		Template:025.0	Template:080 ns	ATA-4
	2	Ultra ATA/33Template:0	Template:033.3	Template:060 ns	ATA-4
	3<ref name="80c">80-conductor cable required</ref>		Template:044.4	Template:045 ns	ATA-5
	4<ref name="80c" />	Ultra ATA/66Template:0	Template:066.7	Template:030 ns	ATA-5
	5<ref name="80c" />	Ultra ATA/100	100Template:0	Template:020 ns	ATA-6
	6<ref name="80c" />	Ultra ATA/133	133Template:0	Template:015 ns	ATA-7
	7	Template:Nobr	167Template:0	Template:012 ns	CompactFlash 6.0<ref>CompactFlash 6.0 Introduction Template:Webarchive</ref>

See also

• PIO—The first interface type used between devices (mainly hard disks) and the computer.
• Parallel ATA
• Serial ATA

References

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