Windows XP: Resetting DMA for CD-ROM drives

Article ID: NN6
Last Updated: December 25, 2001

SUMMARY

CD-ROM and DVD-ROM drives can revert to using PIO mode, despite being set to use "DMA if Available." This article explains how to make Windows XP redetect the DMA capabilities of the drives.

This behaviour occurs with the following conditions:

• Windows XP is the operating system

• A CD-ROM or DVD-ROM drive, which is known to support DMA mode now works only in PIO mode.

• The drive controller is set to use "DMA if available" but reports to be only in PIO mode.

DISCLAIMER

Notorious Networks, its employees, associates and owners can make no warranty about the effectiveness of this workaround. We are not be liable for any damages to software, hardware, data, or finances, that may take place due to the application of this procedure.

RESOLUTION

NOTE: This procedure involves editing the Registry. This should only be attempted by expert users or computer professionals. Editing the registry can cause the computer to become unusable.

1. Open RegEdit

2. Find the following KEY
   
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}\000x

3. The last four digits will be 0000, 0001, 0002, 0003, and so on.

4. Under each key, delete all occurences of the following values:

   1. MasterIdDataChecksum

   2. SlaveIdDataChecksum.

5. Reboot the computer. Windows will now redetect DMA settings.

ACKNOWLEDGEMENT

The solution presented here was contributed by Alexander Grigoriev, as presented on usenet (link to article).

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