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UDMA

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TheUltra DMA(Ultra Direct Memory Access,UDMA) modes were the fastest method used to transfer data through theATAhard diskinterface,usually between the computer and an ATA device. UDMA succeededSingle/Multiword DMAas 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 forCompactFlash), 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 datasettling times,lowerimpedanceand reducecrosstalk.[1]

Transfer Modes
Mode Number Also called Maximum transfer
rate (MB/s)
Minimum
cycle time
Defining
standard
Ultra DMA 0 016.7 120ns 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 CompactFlash6.0[3]

See also

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References

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