How does PCI Interrupt Line get assigned?

NTDEV
1

Can anyone explain the relationship between the PCI INTA, INTB, etc and th
the software (HAL I assume for Windows) assigns the associated Interrupt
Line routing.

The reason I would like to know is our hardware people have designed this
new controller board that uses a PCI transparent bridge. Behind the
pridge is 2 PCI devices. They connected the 2 PCI devices to the same
INTA line expecting that they would get assigned the same interrupt
routing.

What actually happens is that each PCI device behind the transparent
bridge gets assigned it’s own PCI Interrupt Line mapping. This is causing
problems because Windows gets confused on which PCI device is
interrupting.

Thanks
Dave Eaves

2

> Can anyone explain the relationship between the PCI INTA, INTB, etc
and th

the software (HAL I assume for Windows) assigns the associated
Interrupt
Line routing.

Do you mean ACPI or non-ACPI machine?

Max

3

PCI INTA &ct lines to IRQs get mapped by a combination of the ACPI tables
(if this is an ACPI machine) or the MPS tables (if this is an MPS 1.4 spec
machine), or by some BIOS PnP stuff I’m not familiar with for SP machines.

As far as I know, devices on a card specify which PCI INT line the device
uses in the configuration header info for that device. There are also some
rules in the PCI spec about how interrupts should be handled for multiple
devices on a card, if I recall correctly. I never had to get into that side
of the interrupt routiing stuff so I don’t recall exactly how this works.
But I suspect that your problem is either an incorrectly set up PCI
configuration header, or missing an assumption in the PCI spec on how
interrupts route.

Loren

4

ACPI would be good. Both would be better.

-----Original Message-----
From: Maxim S. Shatskih [mailto:xxxxx@storagecraft.com]
Sent: Wednesday, July 09, 2003 8:45 PM
Subject: Re: How does PCI Interrupt Line get assigned?

Can anyone explain the relationship between the PCI INTA, INTB, etc
and th
the software (HAL I assume for Windows) assigns the associated
Interrupt
Line routing.

Do you mean ACPI or non-ACPI machine?

Max

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