"Linux Gazette...making Linux just a little more fun!"

The Answer Guy

By James T. Dennis,
Starshine Technical Services, http://www.starshine.org/

readdress COM port to 3 or 4

From PJ on 25 Jun 1998

can you tell me how to readdress COM port2 to port 3 or 4? I need to use COM port 2 for other device.

No. I can't. You'll want to refer to the documentation that should have come with your hardware (this is almost certainly a hardware issue that is completely unrelated to the OS or software that you're running). The details vary among manufacturer, devices and models.

If you have a couple of COM ports built into your motherboard it is possible that you can disable or reset the I/O addresses, IRQ's and other details for your COM ports via the CMOS setup program (the interface through which you set the date and time, the hard drive type and geometry and various other firmware settings that are stored in extra registers of your PC's clock chip --- a chip which uses CMOS technology so that it dissipates very low power consumption and is thus suitable for operation off of a battery while the system is powered down).

This "setup" program is usually (almost always) stored in the system firmware (the BIOS ROM's on your motherboard) and is typically accessible at boot/power-up via some system dependent keystroke. Usually there is a message that is briefly displayed to note what the magic keystroke would be --- something like:

"Press <Del> not to enter Setup"

If that doesn't work (either because your COM ports are not on your motherboard or for other reasons) you can open up the case and look at the various DIP and/or "berg" (jumper pins) settings that you'll find. Some of them may be labelled. There might also be a manufacturer's mark that might lead you to a website or phone number where you can get support and documentation for the device.

If you can't find any documentation for some cheap multi-function (IDE, floppy, COM, and parallel port) card --- your best bet is to buy a new one (typically $10 to $35 US) and toss the old one into a drawer as an emergency spare.

As a final note: please consider what it's like to answer such a question. You give no details about what sort of system you have, what you've tried (do you have any docs, have you looked at them), what device you're trying to add (odd that it must be on COM2 --- how do you know that), what OS distribution and software you're running, etc.

You send a two line question which cannot be reasonably answered in less than fifty. In IRC and on most newsgroups and mailing lists you'd either be ignored or flamed. We're all volunteers here and the one thing we ask is that you do your homework before you post.

I'm not saying this just to sound crabby (if I was going to be irate, I'd've just deleted this). If you don't do your homework --- and put considerably more thought and energy into your questions than you won't get any satisfaction out of the Linux community.

Copyright © 1998, James T. Dennis
Published in Linux Gazette Issue 30 July 1998

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