Subject: Re: ioapic and interrupt lines
To: Manuel Bouyer <bouyer@antioche.eu.org>
From: Frank van der Linden <fvdl@netbsd.org>
List: port-i386
Date: 09/09/2005 16:44:14
Manuel Bouyer wrote:

>Hi,
>Does anyone know if an interrupt > 31 is valid on current i386 hardware ?
>>From what I can see in our i386 code, it 0-15 for legacy more, or
>0-31 for ioapic.
>
>  
>
Hey Manuel,

That depends on the ioapic. The theoretical maximum is 255, since 8 bits 
in register 0x01 of an ioapic determine the maximum size. I've not seen 
ioapics with more than 24 lines for normal systems, though.

What's your context? There's also the ACPI "global interrupt number", 
which can be bigger, since it assigns a unique number to all interrupts 
in the system. That can certainly be bigger than 31, though it's 
software only.

- Frank