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PC com ports

To: <ct-user@contesting.com>
Subject: PC com ports
From: sharriso@sysplan.com (Steve Harrison)
Date: Mon, 8 Aug 1994 15:10:09 -0400 (EDT)

On Mon, 8 Aug 1994, Jim Reisert AD1C 08-Aug-1994 1417 wrote:
> Best bet is to buy a PC with two standard COM ports at COM1 (uses IRQ4) and
> COM2 (uses IRQ3).  Then buy a 2 serial port option card that allows you
> configure COM3 on IRQ2 and COM4 on IRQ5.  They sell these boards in the
> states for around $40 - they are made by BOCA and STB.
Actually, the Boca board in particular is less than $16 at several 
vendors in the Washington, D.C. area. In addition, there are several 
vendors of combination IDE-type HD/floppy controller, dual-COM port, one LPT 
port and one game port, all on a single board for $19 or less. 
Unfortunately, there is a very common full-height version of this board whose
COM ports usually don't work properly, although they will show up as fine on 
internal diagnostics tests. I exchanged a pair of these for a pair of 
half-height different manufacturer types, and these seem to work 
properly; the two COM ports may be configured from COM 1 through 4 at any 
IRQ from 1 to 15. The boards never have manufacturer names on them; but 
the vendors know where they came from!

Incidentally, it may not be widely known, but MS Windows 3.1 has a bug 
that causes incorrect default COM-port addresses and IRQ values. I'm not 
sure how to work around this as I just figured it out, then found a note 
regarding the bug on a BBS last night. I suspect the ports are simply 
shifted one higher (that is, COM1 is actually COM2), but the IRQ value is 
for the original IRQ. You can set the IRQ in the Control Panel "Ports", 
and you can also reset the ports' addresses in Control Panel. However, I 
was unable to set things right by correcting the SYSTEM.INI file in the 
C:/WINDOWS directory; the next time I ran windows, the ports were right 
back to the original W3.1 incorrect addresses!

73, Steve KO0U/4 <sharrison@sysplan.com>

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