*BSD News Article 83782


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From: adm2@sarc.city.ac.uk (Alan Messer)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Serial ports and internal modems..
Date: 26 Nov 1996 16:39:05 GMT
Organization: Systems Architecture Research Centre, City University, London, UK.
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Hiya,

My machine comes with 2 serial ports as one would expect sitting on the
usual IO addresses and interrupts (3 & 4).. Just recently I've brought an
internal modem for the machine which has a config to make the modem act as
either COM1-4.. no problem I thinks and I configured the port to COM4 for the
internal modem.. My understanding of this is that it uses a slightly
different IO address to COM2, but the same interrupt.. Before placing this
on my machine I tried it with no problems under my brother's Win95 machine..
No problems..

Now I've come to configure my FreeBSD (2.1.0) box to use the modem.. I
placed a sio line in the config for COM4 and the same interrupt and
recompiled the kernel.. But the new port isn't recognised.. COM3 neither.

On reading the FAQ/Handbook in closer detail it reveals that serial 
ports can't use the same interrupt.. Yet, under DOS this would seen to
be the norm.. So what gives? The internal modem has no config to move the
interrupt (well that's not quite true there are 6 or 7 dips but with no
more documentation than 4 settings for the different COM combinations)..
And my BIOS/motherboard don't allow the interrupts to be changed..

Any ideas?

The internal modem is a plain OEM 33.6 modem using the usual rockwell
chipset.. 

Alan.

-- 
Alan Messer                           | Email: adm2@sarc.city.ac.uk.
Systems Arch., I-Op Research Centre,  | Tel: +44 171 477 8551
City University, London, EC1V 0HB     | Fax: +44 171 477 8587
URL: http://www.cs.city.ac.uk/homes/adm2/