Windows NT Does Not Provide IRQ Sharing (102658)
The information in this article applies to:
- Microsoft Windows NT Server 3.1
- Microsoft Windows NT Workstation 3.1
- Microsoft Windows NT Advanced Server 3.1
This article was previously published under Q102658 SUMMARY
Windows NT does not provide for interrupt request line (IRQ) sharing
unless the machine's hardware supports it, such as machines that use
Micro Channel Architecture (MCA). Unless it is supported by the
machine, you cannot use two IRQs simultaneously, such as devices on
ports COM1 and COM3, which both use IRQ 4.
The ability to share IRQs is hardware dependent. MCA machines are
normally able to share IRQs by default. Although Extended Industry
Standard Architecture (EISA) hardware does have IRQ sharing as part of
its specification, not all EISA machines implement IRQ sharing. Also,
on some implementations of EISA, IRQ sharing must be configured in
order to work. An example of this is Compaq's EISA machines, which are
not configured to share IRQs by default.
Industry Standard Architecture (ISA) machines running Windows NT may
have two devices set up to use the same IRQ with different COM ports,
but only one can have the IRQ or port open. Depending on the devices,
it is possible that either one or both will not operate, or there may
be intermittent problems with devices on the same IRQ.
| Modification Type: | Major | Last Reviewed: | 11/20/2003 |
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| Keywords: | kbHardware KB102658 |
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