Microsoft KB Archive/162167

{| The information in this article applies to:
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 * Microsoft Windows NT operating system version 3.1
 * Microsoft Windows NT Advanced Server version 3.1
 * Microsoft Windows NT Workstation versions 3.5, 3.51, and 4.0
 * Microsoft Windows NT Server versions 3.5, 3.51, and 4.0

SUMMARY
This article outlines the relationship between Windows NT and the new I2O input/output (I/O) controller specification.

What is I2O?
I2O is a specification that allows for intelligent input/output operation. A controller that is compatible with this specification can now support hardware interrupt requests (IRQs) above 15. Current implementations for this specification are appearing in dual-processor, Pentium Pro motherboards by such companies as Micron and SuperMicro. In these new motherboards, the I2O specification is being implemented in two parts: a PCI I/0 controller utilizing an i960 controller, and a software component consisting of a hardware abstraction layer allowing for up to 256 hardware IRQs.

What effect do these additional IRQs have on Windows NT's functionality?
Support for I2O is not implemented directly in Windows NT's kernel. Rather, support for these additional IRQs is being implemented at the individual device driver level. If the device driver is not written to support the higher IRQs, then Windows NT will not use the device.

How can I tell if a device is using an I2O controller?
When you check the I/O properties on the device in Windows NT Diagnostics, it will show an IRQ for that device that is above 15. Windows NT recognizes that it has been assigned the IRQ, it just does not know how to use it.

What can I do if I have a device that is using these higher IRQs but no

device driver has been written to support it?
Three options exist:


 * 1) Disable the I2O controller. This cannot be done on all motherboards.

You will have to check with the manufacturer to determine if this can be done.
 * 1) Contact the manufacturer to see if it has an updated device driver

which supports the new I/O controller.
 * 1) Use a device that does support the controller.

For More Information
For more information on the I2O specification, see: http://developer.intel.com/design/litcentr/litweb/1821a.htm

For more information on the i960 controller, see: http://developer.intel.com/design/litcentr/litweb/i960.htm

The third-party products discussed here are manufactured by vendors independent of Microsoft; we make no warranty, implied or otherwise, regarding these products' performance or reliability.
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Last reviewed: May 5, 1997

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