Article ID: 170922 - View products that this article applies to.
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PCI Overview and Interrupt AssignmentThe PCI specification allows the motherboard manufacturer to determine interrupt assignments. Because there is no single method to assign an IRQ to a PCI device, you may experience problems installing multiple PCI devices in Windows NT.
Programmable Interrupt Controller (PIC):
Every motherboard has a device called the Programmable Interrupt Controller (PIC). This is the central location all devices must use when they wish to be serviced by the central processing unit (CPU). The following is an example of one design:
PCI Int#A (PCI Slot 1)--- |===============| | |Programmable | PCI Int#A (PCI Slot 2)---------| | Interrupt Line to CPU | |Interrupt |========> PCI Int#A (PCI Slot 3)--- | | |Controller | |===============|
A problem with this design is that three PCI devices must share the same interrupt number and line. If any of the cards do not properly pass the interrupt (driver or hardware failure) to one of the other devices requesting attention, one of the cards may fail to be detected or will not be used by a driver.
The following is an example of a newer design:
PCI Int#A (PCI Slot 1)----------|==============| |Programmable | PCI Int#A (PCI Slot 2)----------| | Interrupt Line to CPU |Interrupt |========> PCI Int#A (PCI Slot 3)----------| | |Controller | |==============|
Because each device has their own direct trace to the PIC, this design allows the PIC to assign a different IRQ for each PCI device. This allows assigning virtual IRQ's or allowing each device to have its own discrete IRQ.
TroubleshootingIf the computer fails to boot, there is probably a hardware issue. Please contact the hardware manufacturer for more information.
Perform one of the following steps if the computer boots, but Windows NT states a device failed:
(http://support.microsoft.com/kb/148501/EN-US/ )Preventing PCI Resource Conflicts on Intel-Based Computers
Article ID: 170922 - Last Review: October 31, 2006 - Revision: 1.1
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