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Date: Fri, 12 Jul 1996 09:02:11 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199607112302.JAA18895@godzilla.zeta.org.au>
To: freebsd-hackers@FreeBSD.ORG, j@uriah.heep.sax.de
Subject: Re: sio / modem problems
Cc: graichen@axp5.physik.fu-berlin.de, tom@sdf.com
Sender: owner-hackers@FreeBSD.ORG
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>>   You shouldn't put devices on irq 2, as it is used to cascade irqs 8
>> through 15
>> 
>>   irq is only safe on a XT, which has only one irq controller.

>Only partially right.

>The ISA bus line for IRQ2 is connected to the second IRQ port of the
>slave PIC, thus known as IRQ9.  So you have to configure your card to
>IRQ2, but your software (kernel) to IRQ9.

Only partially right :-).

Config has a kludge in to to map IRQ2 to IRQ9, so that people don't
need to know about this complication.  Config complains about the
misconfiguration so people should know about this problem if they
use IRQ2.

Bruce