Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!pacbell!att!cbnewsh!mbb
From: mbb@cbnewsh.ATT.COM (martin.b.brilliant)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Activating COM3 and COM4
Message-ID: <372@cbnewsh.ATT.COM>
Date: 2 May 89 20:02:47 GMT
References: <8036@fluke.COM>
Distribution: na
Organization: AT&T Bell Laboratories
Lines: 27

From article <8036@fluke.COM>, by lal@tc.fluke.COM (Larry Lohkamp):
> ..... The AST board
> came with two ports at COM1: and COM2:. My serial board says that its
> two ports can be used as COM1, 2, 3, or 4. I tried all possible 
> combinations of assigning the two interrupts ( #3 and #4 ), but could not
> get the machine to recognise anything but COM1 & 2. If it makes any
> difference, my DOS rev. is 3.3. Can I get all 4 ports to work, or am I
> dreaming the impossible?

I had a similiar problem with an internal modem.  The modem is supposed
to be configurable as any of the four COMn: ports.  The documentation
for DOS 3.3 says that DOS recognizes four COMn: ports.  However, the
documentation for the modem points out that the DOS definition of COM3:
and COM4: is not the one used by older communications software, and
that the board is compatible with the old software, not with DOS.

Some of this "older communications software" is explicit about how
COM3: and COM4: are defined in terms of port address and IRQ line. 
However, I couldn't find anything that says how DOS defines these
ports.  Can someone provide definitive information about this?

M. B. Brilliant					Marty
AT&T-BL HO 3D-520	(201) 949-1858
Holmdel, NJ 07733	att!hounx!marty1 or marty1@hounx.ATT.COM

Disclaimer: Opinions stated herein are mine unless and until my employer
	    explicitly claims them; then I lose all rights to them.