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From: webb@ibmpa.awdpa.ibm.com (Bill Webb)
Newsgroups: comp.sys.ibm.pc.rt,comp.sys.ibm.pc.hardware
Subject: Re: PC RT hardware questions
Message-ID: <1990Nov30.132924@ibmpa.awdpa.ibm.com>
Date: 30 Nov 90 21:29:24 GMT
References: <1990Nov16.210555.1322@ultra.com> <1990Nov14.004522.i@> <1990Nov22.155240.26006@watdragon.waterloo.edu>
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Reply-To: webb@ibminet.awdpa.ibm.com (Bill Webb)
Organization: IBM AWD Paloalto
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In article <1990Nov22.155240.26006@watdragon.waterloo.edu>,
smvorkoe@daisy.waterloo.edu (Stefan M. Vorkoetter) writes:
|> 
|> The RT we have has two serial ports on the motherboard (planar in
IBM
|> wording).  We also have a four port ASYNC adapater, giving us a
total
|> of six ports.  Can I now plug in a standard AT 2 port serial card?
If
|> so, will there be any conflicts with interrupts and such.  I suspect
|> that the slots are AT compatible, but that it is not really a bus.
In
|> other words, each slot is separate, and two identical cards plugged
|> into different slots will not necessarily interfere with one
another.
|> Stefan Vorkoetter

Yes you can plug in most AT cards. The RT has essentially an AT bus (not
quite
but close enough for this discussion). If the AT cards are at COM1 and
COM2 then they will be /dev/ttyc0 and /dev/ttyc1 (assuming you are 
running BSD 4.3 which I expect you would be at an educational
institution).
If you don't have these devices on the system you can make them 
(after rebuilding your kernel if you didn't config in asy4 and asy5),
by issuing the following commands (as root):
	cd /dev
	./MAKEDEV com0 com1

The RT can handle shared interrupt lines (provided that the cards
do the "right" thing (which I suspect many AT cards don't). The best
thing for safety and efficiency is to put AT cards on their own 
interrupt (IRQ) line. This is usually not a problem with COM cards
as they are on IRQ 3 and 4 (if memory serves me), and most RT cards
are not (most that can be on 3 or 4 (such as the ethernet card)
have jumpers that can change it if needed). In any case, the bus is
really a bus - you cannot have cards with conficts in IO ports or 
IO memory addresses and expect things to work. As I already mentioned
RT
cards can share IRQ lines but you usually don't have to.

Note that if you need additional serial ports (above adding the two
via an AT card) you can add additional 4port cards with different
port addresses. The asy driver supports up to 4 4-port cards for a
total of 18 ports (2 plannar plus 16 on the cards). Of course you 
might start to run out of slots if you do that (the disk adapter,
network 
adapter, and display adapter all take slots).

----------------------------------------------------------------
The above views are my own, not necessarily those of my employer.
Bill Webb (IBM AWD Palo Alto), (415) 855-4457.
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