From: Steve VanDevender (stevev@miser.uoregon.edu)
Date: 05/31/93 

From: stevev@miser.uoregon.edu (Steve VanDevender)
Subject: Re: [Q] Serial ports 0/2 and 1/3 don't work at the same time
Date: 31 May 1993 19:04:35 GMT

I fought this problem a couple of weeks ago. I set up my three
serial ports with standard IRQ assignments and found that COM1
and COM3 on IRQ4 conflicted. The only solution is to change the
IRQ assignments so that all serial devices you intend to use
simultaneously have different IRQs. In my case I was able to
rejumper COM1 to IRQ 5.

You will probably also have trouble with running both parallel
printers on IRQ 7 at the same time.