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Date:      Wed, 27 Aug 1997 09:59:35 -0400 (EDT)
From:      Chuck Robey <chuckr@glue.umd.edu>
To:        Adam Baran <badam@zimw.gdynia.pl>
Cc:        freebsd-hackers@FreeBSD.ORG
Subject:   Re: SIO driver question
Message-ID:  <Pine.BSF.3.96.970827095346.293A-100000@Journey2.mat.net>
In-Reply-To: <Pine.BSF.3.96.970827144307.1829A-100000@kilo.zimw.gdynia.pl>

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On Wed, 27 Aug 1997, Adam Baran wrote:

> Hi,
> 
> Here is my question:
> Is it possible to configure (or hack ;)) SIO driver to make it work with
> COM2 and COM4 devices occupying the same IRQ line (namely IRQ3) ???
> 
> Background:
> I use mouse on COM1, baseband modem on leased line on COM2 (to ISP).
> COM1 and COM2  are motherboard builtin COMs.
> I'd like also to configure internal ZOOM FCV9425 modem to work as callin
> device. Problem is that I can only jumper the modem to occupy specific COM
> port (namely 1,2,3 or 4) but can't change IRQ beyond defaults.
> 
> So, maybe someone could help me with SIO configuration or simply tell:
> "this is impossible'.

If you're talking about getting two serial devices to cooperate in sharing
the same interrupt, no, it's not possible without a card specifically
designed for that sharing, like a Digiboard or Boca card.  Basically, the
ISA bus doesn't allow sharing of IRQ's.  It works on dos because the other
ports aren't actually hooked up to executing code when you aren't using
them, but on Unix of any kind, they are all hooked up to executing drivers
at all times, and you cannot share irq's. 

You get folks once in a while, even on this list, who claim it isn't so.
These are the same people who claim there's no reason why their sound
cards or printer ports don't work correctly (whatever they've purposely or
inadvertently shared).

> 
> Thanks in advance.
> 
> 
> 
> 

----------------------------+-----------------------------------------------
Chuck Robey                 | Interests include any kind of voice or data 
chuckr@eng.umd.edu          | communications topic, C programming, and Unix.
213 Lakeside Drive Apt T-1  |
Greenbelt, MD 20770         | I run Journey2 and picnic, both FreeBSD
(301) 220-2114              | version 3.0 current -- and great FUN!
----------------------------+-----------------------------------------------




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