Microsoft KB Archive/940394

= The IRQ for a device appears as a negative number in Device Manager on a computer that is running Windows Vista =

Article ID: 940394

Article Last Modified on 8/4/2007

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APPLIES TO


 * Windows Vista Home Premium
 * Windows Vista Home Premium 64-bit Edition
 * Windows Vista Enterprise
 * Windows Vista Enterprise 64-bit Edition
 * Windows Vista Business
 * Windows Vista Business 64-bit Edition
 * Windows Vista Home Basic
 * Windows Vista Home Basic 64-bit Edition

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SYMPTOMS
On a computer that is running Windows Vista, you view resources by type in Device Manager. When you expand Interrupt request, the interrupt request (IRQ) for one or more of the devices that are listed may appear as a negative number.

For more information about how to see the devices that are listed under Interrupt request in Device Manager, see the &quot;More Information&quot; section.



CAUSE
This issue can occur if a device uses Message Signaled Interrupts (MSI).



MORE INFORMATION
MSI is supported in the PCI Local Bus Specification, Revision 2.2 standard and in later versions. MSI is the native interrupt mechanism for devices that are connected to a PCI Express bus or to a PCI-X bus. MSI requires Advanced Programmable Interrupt Controllers (APICs).

To see the devices that are listed under Interrupt request in Device Manager, follow these steps:
 * 1) Start Device Manager.
 * 2) Click View, and then click Resources by type.
 * 3) Expand Interrupt request.

