Path: utzoo!utgpu!attcan!uunet!jetson!john
From: john@jetson.UPMA.MD.US (John Owens)
Newsgroups: comp.unix.microport
Subject: Re: Mail to uport doesn't work
Summary: I/O ports
Keywords: mail, microport
Message-ID: <165@jetson.UPMA.MD.US>
Date: 3 Nov 88 15:26:38 GMT
References: <4893@b-tech.ann-arbor.mi.us> <134@twwells.uucp> <378@mccc.UUCP> <4154@pbhyf.PacBell.COM>
Organization: SMART HOUSE Limited Partnership
Lines: 23

In article <4154@pbhyf.PacBell.COM>, kjk@pbhyf.PacBell.COM (Ken Keirnan) writes:
> The "/dev/lp" entry comes linked to "/dev/lp0".  Try, in turn, outputing
> a string (like "echo Hello there") to /dev/lp1 and /dev/lp2.

In case anyone wonders what's behind this:

Parallel ports on PCompatibles typically use one of three I/O port
base addresses:  03BC, 0378, and 0278 (hex).  The ROM BIOS searches
for parallel ports at these three addresses, and places the ones it
finds, in order, in a table in RAM.  The first one it finds becomes
LPT1 (as referred to by DOS), the second one LPT2, and the third LPT3.
So if you only have one printer port, it will always be LPT1 under
DOS.

The microport drivers (apparently) and the SCO Xenix drivers have lp0,
lp1, and lp2 always associated with the three fixed port addresses.  I
like the microport/Xenix way myself, but I tend to keep track of which
ports my cards are on.  I suppose the way the BIOS (and therefore DOS)
does it is better for people who don't.

-- 
John Owens		john@jetson.UPMA.MD.US		uunet!jetson!john
+1 301 249 6000		john%jetson.uucp@uunet.uu.net