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Force Windows to Reexamine the DMA Capabilities of Devices

Filed under: PC Speed 

When you install Windows XP or Windows Vista, the operating system will examine all attached IDE devices for their capabilities and configure them accordingly. This is critical in ensuring a fast computer, since the hard disks and DVD drives need to operate at maximum performance.

In some cases this automatic detection of the capabilities of attached devices fails and you will end up with a slow computer. Especially with today’s large hard disks and use of DVD instead of CDROM, maximum transfer rates are very important. If you are not sure if the devices have been configured properly, you can force Windows to reexamine the DMA capabilities of Devices. This will ensure that attached devices are checked again and configured properly.

Follow these steps to force Windows to reexamine the attached IDE devices:

  1. Start the Registry Editor.From the Windows Start menu, select Run. In the Run box, type regedit and click OK.
  2. In the Registry Editor, locate the following key:
  3. Under this key you will see sub-keys with the values “0000”, “0001”, “0002” and so on. In each of these sub-keys, delete the entries named: MasterIdDataCheckSum and SlaveIdDataCheckSum. Right-click the value and in the popup menu select Delete.
  4. Close the Registry Editor. Select Exit from the File menu.
  5. Now restart your computer.

During the next boot, Windows will reexamine the DMA capabilities of the attached IDE devices and configure the devices accordingly. This should fix any incorrect DMA configuration of your hard disks and optimize your PC for performance.

Force Windows HDD DMA check

After this, make sure you also check the actual DMA enable setting for the IDE Channel device in the Device Manager.

If all this does not work, and you are sure the hardware should support the DMA option, then try checking the device drivers for your I/O controllers. Mostly these are part of the chipset drivers for the computer. You can automatically check if you have the latest version using a driver program for example.

Just keep in mind that there are cases where the DMA option needs to be enabled in the BIOS first (even just for secondary channels) before Windows can use it.
Another possible problem is that the IDE cable is either too long or not the 80-wire type. That can causes problems which makes the mode fall back to PIO.
The last thing you can check if you are on XP is a Microsoft article about multiple time-out or CRC errors causing the system to fall back on PIO from DMA.



3 Comments to “Force Windows to Reexamine the DMA Capabilities of Devices”

  1. Mytch says:

    When I open the 3 folders, 0000, 0001, & 0002, the only things in these folders is,under the tab NAME- ‘ab’icon with the word (default) right next to the icon. Under the tab TYPE, it says “REG_SZ”, and under the tab DATA, it says “(value not set)”. I’m trying to increase my computer speed. I’m running a PC w/Windows XP Home Edition, Intel Pentium 4, 2.40GHz, 1.00GB. I use this for my home recording studio. I just installed a second internal drive, Seagate IDE, 7200rpm, 400GB. I’m using Pro Tools 6.4 LE for my studio. What do I do with the DMA values that are/are NOT shown?

  2. Steve says:

    My laptop with a long history has prim and sec showing on 001 and 002. But it also has prim and sec on 012 and 013. Trying every trick on either won’t restore HDD DMA. One idea is to delete all keys for ide. So I deleted all 4. Reboot was successful, but omitted 001 and 002 entirely, and restored 012 and 013 with few of the expected subkeys. Still worked, but still PIO only.

  3. Anthony says:

    @Steve – I updated the article with some more info.
    In your situation, you can check the BIOS settings to see id DMA is enabled for the ATA/IDE controller(s).
    The cable will not be applicable in a laptop of course.

    Did you ever see the DMA enabled in the past though?

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