How do I enable Bus Mastering in Windows NT?

A. Windows NT 4.0 has native bus mastering support with Service Pack 3. To enable bus mastering in Windows NT 4.0 perform the following:

  1. Ensure you have Service Pack 3 installed and you have the Service Pack 3 CD-ROM
  2. Run the DMACHECK.EXE utility in support\utils\i386\ directory of the CD-ROM or download from
  3. When DMACHECK.EXE is run, it will indicate whether DMA is enabled on either IDE channel. Click on the Enabled radio button to enable DMA for each drive and any other DMA-capable devices in the system.
  4. Reboot the system.
  5. Execute the DMACHECK utility again to check that DMA was enabled.
  6. If the drive is DMA-capable and DMA is not enabled at this point, this failure must be corrected before proceeding

The DMACheck util uses a registry setting - 0 is for disabled, 1 is for enabled, but if you enter 2 as the setting it will force NT to use DMA if the hardware supports it. You may get better performance from drivers supplied with the motherboard rather than the DMACHECK.

So Intel and Microsoft do officially support DMACHECK. See also

DMACHECK.EXE IDE BusMaster is very important : you can read or write on disk without using 100% of CPU (like SCSI)

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