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=                                UDMA                                =
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                             Introduction                             
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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.

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

Transfer modes
Mode || Number || Also called || Maximum transfer rate (MB/s) ||
Minimum cycle time || Defining standard
rowspan=8 | 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 	 	 44.4	 45 ns 	 ATA-5
4 	Ultra ATA/66	 66.7	 30 ns 	 ATA-5
5 	Ultra ATA/100	 100	 20 ns 	 ATA-6
6 	Ultra ATA/133	 133	 15 ns 	 ATA-7
7 	  	 167 	 12 ns 	 CompactFlash 6.0


                               See also                               
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* PIO--The first interface type used between devices (mainly hard
disks) and the computer.
* Parallel ATA
* Serial ATA


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Original Article: http://en.wikipedia.org/wiki/UDMA


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