Clarification of Enhanced IDE Under Windows NT
ID: Q141591
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The information in this article applies to:
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Microsoft Windows NT Workstation versions 3.5, 3.51, 4.0
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Microsoft Windows NT Server versions 3.5, 3.51, 4.0
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 third-party 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. 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.
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.
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.
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.
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.
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.
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.
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.
Additional query words:
prodnt ATA2 ATA tertiary
Keywords : ntsetup
Version : winnt:3.5,3.51,4.0
Platform : winnt
Issue type : kbinfo