UDMA

For the main article about the interface, see Parallel ATA.

The Ultra DMA (Ultra Direct Memory Access, UDMA) modes were the fastest method used to transfer data through the ATA hard disk interface, usually between the 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]

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]
  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
  2. ^ a b c d 80-conductor cable required
  3. ^ CompactFlash 6.0 Introduction Archived 2010-11-21 at the Wayback Machine