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Date: Thu, 11 Jul 1996 09:45:22 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199607102345.JAA00264@godzilla.zeta.org.au>
To: ejs@bfd.com, terry@lambert.org
Subject: Re: Some recent changes to GENERIC
Cc: SimsS@infi.net, davidg@Root.COM, dawes@rf900.physics.usyd.edu.au,
        hackers@FreeBSD.org, jgreco@brasil.moneng.mei.com, jkh@time.cdrom.com
Sender: owner-hackers@FreeBSD.org
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>While I agree that a lot of people don't bother avoiding interrupt
>conflict, I have to disagree with the software not allowing for it.  I
>honestly can't remember a single program from 5 years of consulting that
>allowed for com 3 without letting me specify what IRQ com 3 was on.  Even
>Win3.1 (can't speak for older versions) can be set, just not easily.

Even FreeBSD can be set, just not easily:

1. reboot
2. enter -c at the boot prompt
3. change the config to get interrupts on the ports that you want to use,
   e.g.:
   irq sio0 -1		# no irq, i.e., polled mode for sio0
   irq sio1 -1		# no irq, i.e., polled mode for sio1
   irq sio2 4		# if necessary
   irq sio3 3		# if necessary
   or:
   disable sio0
   disable sio1
   irq sio2 4		# if necessary
   enable sio2
   irq sio3 3		# if necessary
   enable sio3

Polled mode is good enough up to 9600 bps if the UART is a 16550.  It is
just as good as completely disabling the port if the port isn't used.

Bruce