Clarification of Enhanced IDE Under Windows NT

 Last reviewed: January 22, 1996
Article ID: Q141591
The information in this article applies to:
  • Microsoft Windows NT Workstation versions 3.5 and 3.51
  • Microsoft Windows NT Server versions 3.5 and 3.51

SUMMARY

This article provides clarification of issues relating to EIDE devices under Windows NT. It addresses the most common questions asked by customers.

MORE INFORMATION

Q: What is the maximum amount of IDE devices Windows NT will support?

A: Section 2.3.1.1 of the EIDE Version .95 Guide defines the maximum amount 

   to 4 devices, 2 devices on each channel. The Windows NT ATAPI.SYS driver
   conforms to this standard.
Q: What about adding a 3rd IDE channel for more than 4 devices?

A: Currently there is no specification for this. Thus, it is unsupported by 

   Windows NT. Some sound card manufacturers have recently put actual ATA-2
   controllers on their sound cards, these manufacturers would have to
   release a new ATAPI.SYS driver for this to work under Windows NT as a
   3rd channel, but would still be unsupported.

   They would be supported if the ATA-2 controller on the sound card was
   configured as the secondary channel in absence of one already present.
Q: What modes of transfer can Windows NT do with IDE devices?

A: Windows NT 3.5 and 3.51 currently support PIO Mode 1 and 2 only.

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 Section 2.3.1.1 of the EIDE guide states that
   high speed PIO or DMA transfers is recommended, but is NOT REQUIRED for
   the secondary channel.

   This is why hard drives should only be put on the secondary channel if
   you need to add a 3rd IDE hard drive

   Many of the high speed features of Enhanced IDE such as Busmastering,
   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
   lower the maximum transfer speed to the slowest device.

KBCategory: kbsetup
KBSubcategory: ntsetup
Additional reference words: prodnt 3.51 ATA2 ATA

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Last reviewed: January 22, 1996
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