Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!oliveb!felix!dhw68k!feedme!doug
From: doug@feedme.UUCP (Doug Salot)
Newsgroups: comp.unix.microport
Subject: Re: com3 & com4 -> tty2 & tty3
Message-ID: <329@feedme.UUCP>
Date: 29 Apr 89 16:24:38 GMT
References: <243@kralc.UUCP> <42700009@osiris.cso.uiuc.edu> <9255@wb3ffv.UUCP> <682@micropen>
Reply-To: doug@feedme.UUCP (Doug Salot)
Organization: Feedme Microsystems, Orange County, CA
Lines: 20

>> > >You can not use IRQ2 for anything under Unix - it is already used by the
>> > >system.
>> > 
>!  I would also like to hear why you can't!
>
>If you have a PC/AT style bus, IRQ2 is not even a valid bus signal!
>Thus, a guess, is that you are not using a true AT bus compatible machine
>or *your driver is polling* and not using the interrupt for a d*mn thing!

(I thought I already posted an explanation; guess it didn't go out.)

Look at the bus signals again.  IRQ 2 on the PC (or XT) is mapped to
IRQ 9 on the AT.   If you have a device that uses IRQ 2, simply tell
the driver to expect interrupts on IRQ 9.

The real AT IRQ 2 is used to cascade the second interrupt controller,
giving you 15 interrupt lines on an AT versus 8 on a PC.
-- 
doug@feedme.UUCP || ...{zardoz,dhw68k}!feedme!doug || doug%feedme@uunet.uu.net
Doug Salot,  The Poor Man's Renaissance Man  (I read *all* of the newsgroups.)