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Thread: Whats the difference between ATA 100 and Ultra DMA?

  1. #1
    Junior Member
    Join Date
    Oct 2001

    Whats the difference between ATA 100 and Ultra DMA?

    Is it the same thing?
    My motherboard supports:
    Ultra DMA 33
    Ultra DMA 66
    Ultra DMA 100

    I am looking to buy a HD, most interfaces say:
    Interface Type DMA/ATA-100 (Ultra)

    Will this be compatible with my motherboard?
    To my knowledge DMA is just what ATA does? So basically the interface type above is an Ultra ATA 100 that uses DMA?

  2. #2
    Join Date
    Jun 2001
    Earth, Milky Way Galaxy, the Universe
    I'm pretty sure that UDMA is just another name for ATA-100, but I might be wrong...

  3. #3
    Junior Member
    Join Date
    Oct 2001
    Yuma, Arizona, USA


    Ultra DMA (Ultra Direct Memory Access) is a protocol developed by Quantum Corporation and Intel for disk drives that enables the computer to take advantage of the fast Ultra ATA disk drives. UDMA/33 is twice as fast as the previous disk drive standard for PCs, supporting burst mode data transfer rates of 33.3 MBps. A further improvement is UDMA/66. Even better than that is the newest UDMA/100. In short, UDMA is a protocol, not a speed.

    Shawn Sonnentag
    IRIX/Linux System Administrator
    ...oh, and Windoze too...

  4. #4
    Join Date
    Sep 2001
    Vancouver, BC Canada
    Yep, you got it right. If your new drive supports ATA100 it also supports UDMA100.

    Most if not all newer ATA33/66/100 drives are UDMA capable.
    ATA and UDMA aren't the same thing but are closely related.

    You could have an ATA33/66/100 drive installed properly and recognized as ATA33/66/100 by the BIOS and still not have UDMA enabled.

    You'll have to go to Integrated Peripherals in the BIOS and make sure IDE Primary Master UDMA and IDE Primary Slave UDMA are set to AUTO to enable UDMA. Usually, setting everything here to AUTO works best. Also, you'd have to go to Device Manager in Windows and enable DMA for your drives.

    Some definitions:

    ATA (AT Attachment): ATA defines the physical, electrical, transport, and command protocols for the internal attachment of storage devices.

    (U)DMA: (Ultra)Direct Memory Access - don't have an exact definition but basically means the cpu doesn't have to do as much work because it has direct access to memory (ram) without having to process data twice.

    Bonus definition:

    ATAPI (AT Attachment Packet Interface) device: A device implementing the Packet Command feature set.
    Last edited by JohnE.; 10-09-2001 at 07:42 PM.
    But, it goes to 11

  5. #5
    Ultimate Member otheos's Avatar
    Join Date
    Nov 1999
    Cardiff, Wales, UK
    A lengthy discussion over this was here

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