Clarification of Enhanced IDE Under Windows NT 4.0

• Microsoft Windows NT Workstation version 4.0
• Microsoft Windows NT Server version 4.0

SUMMARY

This article provides clarification of issues relating to enhanced integrated development environment (EIDE) devices under Windows NT 4.0. It addresses the most common questions asked by customers and hardware vendors.

MORE INFORMATION

1. Q. Is bus-mastering IDE disk access (DMA 0 & 2) available under Windows
      NT 4.0?

   A. This feature is planned for release in the Service Pack 1 or 2 for
      Windows NT 4.0.

2. Q. Does Windows NT use 32-bit I/O accesses (also known as HDD Block
      Mode)?

   A. To date, this has been seen to corrupt data in some cases.
      Therefore, it is not used.

3. Q. Does Windows NT support Advanced PIO/DMA programming modes (PIO Mode
      3 or 4)?

   A. If the BIOS programs the part for advanced PIO modes, then it is
      left in those modes.

4. Q. Does Windows NT support multiple sector disk transfers for hard
      drives and removable media devices such as Ez-Drive, ATAPI Jaz, or
      ATAPI Zip drives?

   A. Windows NT 4.0 supports multi-sector transfers for hard drives,
      CD-ROM drives, and for removable media.

5. Q. Does Windows NT support ATAPI CD-ROM drives supporting DMA and
      multiple sector disk transfers?

   A. This feature is currently in Windows NT 3.51 and 4.0.

6. Q. Does Windows NT have the ability to boot from a drive other than a
      floppy or hard drive device (also called El Torrito capability)?

   A. El Torrito is supported under NT 4.0 for both ATAPI and SCSI
      formats.  The bios must be capable of using El Torrito in
      NonEmulation mode.

7. Q. What is the recommended configuration for my IDE devices?

   A. You should put your hard drives on the primary channel, and your
      slower devices (such as IDE CD-ROMs or IDE tape drives) on the
      secondary channel. This is because high speed PIO or DMA transfers
      are recommended, but are not required for the secondary channel.

      The other benefit of this configuration is that both channels can
      operate simultaneously. This is not the case if two IDE devices are
      on the same chain, because they must alternately share the
      interrupt.

      Many of the high speed features of Enhanced IDE such as bus-
      mastering, DMA scatter/gather transfers, 32-bit PIO transfers, and
      high speed DMA transfers, are not required and not present on the
      secondary channel.

      Many of the current Enhanced IDE controllers do not support separate
      transfer speeds of the slave and master, so if you have a fast
      master device and a slow slave device on the same channel, your
      controller may reduce the maximum transfer speed to the speed of
      slowest device.