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Thread: Turn Direct Memory Access (DMA) on or off

  1. #1
    nitinagarwal1988's Avatar
    nitinagarwal1988 is offline Microsoft MVP
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    Lightbulb Turn Direct Memory Access (DMA) on or off

    Direct memory access (DMA) is a feature that allows certain hardware units such as hard disks to access system memory for reading and/or writing independently of the central processing unit. Many hardware systems use DMA including disk drive controllers, graphics cards, network cards and sound cards. Computers that have DMA channels can transfer data to and from devices with much less CPU overhead than computers without a DMA channel.

    Direct memory access (DMA) is usually turned on by default for devices such as hard disks and CD or DVD drives that support DMA. However, you might need to turn on DMA manually if the device was improperly installed or if a system error occurred.

    In Windows 7 you can turn DMA on or off according to your requirements. Follow the simple steps to do so, you must be logged on as an administrator to perform these steps:

    1. Open Control Panel and then open Device Manager.* If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
    2. Double-click or expand IDE ATA/ATAPI controllers.
    3. Under IDE ATA/ATAPI controllers, for each item that has the word Channel as part of its label, right-click the item, and then click Properties.
    4. Click the Advanced Settings tab. Under Device Properties, select or clear the Enable DMA check box and then click OK.




  2. #2
    Matrix's Avatar
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    Forgive my ignorance, but why or when would one want to consider turning off this DMA thingy?

  3. #3
    nitinagarwal1988's Avatar
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    Sometime when you have an older hardware or may be we can say a scratched CD or DVD, DMA would not let the user perform operations on it. so by turning it off, you revert to PIO mode (Programmed Input-Output, where the central processor transfers data byte for byte or word for word), this may be slow but let you copy or recover most of the data from that disc.

    That's why sometimes it is necessary to turn off DMA.

  4. #4
    riteshtechie's Avatar
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    Thanks Nitin for the explanation, I too was wondering why would someone want to do that.
    Now I gotta try this on with my Scratched DVD's

  5. #5
    whs's Avatar
    whs
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    Hmm, my system must be somehow retarded - no trace of DMA. Is there a setting in e.g. the BIOS one has to make?


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