UDMA Knowpia

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.

Modes faster than UDMA mode 2 require an 80-conductor cable to reduce data settling times, lower impedance and reduce crosstalk.^[1]

Transfer Modes
Mode	Number	Also called	Maximum transfer rate (MB/s)	Minimum cycle time	Defining standard
Ultra DMA	0		16.7	120 ns	ATA-4
	1		25.0	80 ns	ATA-4
	2	Ultra ATA/33	33.3	60 ns	ATA-4
	3^[2]		44.4	45 ns	ATA-5
	4^[2]	Ultra ATA/66	66.7	30 ns	ATA-5
	5^[2]	Ultra ATA/100	100	20 ns	ATA-6
	6^[2]	Ultra ATA/133	133	15 ns	ATA-7
	7	Ultra ATA/167	167	12 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
^ ^a ^b ^c ^d 80-conductor cable required
^ CompactFlash 6.0 Introduction Archived 2010-11-21 at the Wayback Machine

[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

[80c-2] 80-conductor cable required

[3] CompactFlash 6.0 Introduction Archived 2010-11-21 at the Wayback Machine

[1]

[2]

[3]

Summary

See also

References