Re: SMP interrupt patches..

Philip Blundell (
Fri, 23 Jan 1998 11:22:30 +0000

>No, each PCI slot has 4 different IRQ lines (IntA - IntD), although
>usually only one is actually used (and almost always it is IntA, although
>I think anything that claims to be PCI-compliant has to be able to change
>it with the PCI config space).

No, not quite. Any single-function PCI device must use INTA if it generates
interrupts. A multiple-function device is allowed to use INTB or even more
lines _in addition_, but you must always start at the lowest one and work up.

This, combined with the rotation between different slots, means that you get a
reasonable distribution of interrupts to physical IRQ lines.