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Thread: IDE DMA modes

  1. #1
    Uranium Lounger
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    IDE DMA modes

    I've found that all four of my IDE devices (two HDDs, one DVD writer and a DVD reader) have slipped into Multi-Word DMA Mode 2 for no obvious reason. I've removed the Bus Master driver and reinstalled - no joy. I've also done that and gone a step further, deleting the relevant registry entries at HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlCl ass{4D36E96A-E325-11CE-BFC1-08002BE10318} and rebooting. Still no love!

    I have a hard time believing that it's the IDE cables that have gone south - that would be two at the same time. Any ideas as to what, other than a hardware failure of some kind with the controller, could cause this to happen on all drives?
    -Mark

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    Re: IDE DMA modes

    As an adjunct, I wanted to share some interesting information that alas, did not solve the problem. Below is listed a table of values that are valid for the corresponding registry entry. Changing these results in Device Manager showing the mode as listed, but after a reboot... everything is back to Multi-Word DMA Mode 2.

    Registry key:

    HKLMSystemCCSControlClass{4D36E96A-E325-11CE-BFC1-08002BE10318}

    0000 - The IDE controller itself
    0001 - Primary channel
    0002 - Secondary channel

    Allowed DWORD values for MasterDeviceTimingMode/SecondaryDeviceTimingMode:

    <pre>Mode Hex Value
    ----------------------------------
    UDMA 6 (Ultra ATA 133) = 10010
    UDMA 5 (Ultra ATA 100) = 10010
    UDMA 4 (Ultra ATA 66) = 8010
    UDMA 3 = 6010
    UDMA 2 = 2010
    PIO Only = 10
    Multi-word DMA Mode 2 = 410 (For most burners)
    Multi-word DMA Mode 1 = 210</pre>


    Perhaps this will be of use to someone... I could not find a definitive listing anywhere, so these are derived from direct experimentation.
    -Mark

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    Re: IDE DMA modes

    Mark,
    How did you determine that they changed modes?
    Curious.
    BOB
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    Re: IDE DMA modes

    Mostly by being vigilant. I recently installed a new hard drive, which I checked in Device Manager post-install and it was operating in UDMA 5 mode. The secondary hard drive, which was previously installed, also ran in that mode. Then I began to notice odd things happening: Nero would create "stuttering" audio CDs that were created from MP3 files, and DVD playback resulted in the audio track getting out of synch with the video over time. I went back to check all of the basic settings before running drive tests and lo and behold, there were all four IDE drives running in Multi-Word DMA Mode 2.

    As you can see from my previous post, directly editing the registry only changed the setting until a reboot. For some reason I cannot fathom, all IDE devices are being detected as Multi-Word DMA 2 even though they should not be.

    My suspicion now is that the hard drive that was failing and subsequently replaced my have damaged the onboard controller. Prior to the new drive and a clean install of Windows, I had that one drive continually slipping back into PIO mode, which meant dreadfully slow transfer times and high CPU usage.
    -Mark

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