COM Port not showing in DM

[FastLearner]

Hello. I have a quick question to which someone here may have a logical explanation.

One of our employees uses a Fujitsu-Siemens E8110 Lifebook notebook PC. It has one RS232 port. This port is listed in DM as Com 1, and it is the only one listed.

He also uses a lot of different software that automatically detect available Com ports, and they all have one common denominator - they all detect a Com Port 3 as being ready and available.

My question is what could Com 3 be, and why is it not being recognized by Windows XP Pro?

Thanks for any help.

-FL

[Sylvander]

Sounds like a BIOS Setup configuration problem.

Looking at the mobo manual for my older PC...

Integrated Peripherals Setup Menu

a. Onboard Serial Port 1 : 3F8/IRQ4
b. Onboard Serial Port 2 : 2F8/IRQ3

Settings available for above are...
a. COM4/2E8, COM3/3E8, COM1/3F8, Disabled.
b. COM3/3E8, COM4/2E8, COM2/2F8, Disabled.

[FastLearner]

Thanks Sylvander,

Yes, but there is only one COM port on the PC, and it is showing up fine in Device Manager. I've been thinking: could a modem, for example, automatically be assigned a COM port, and it (the port being used) not show up under DM?

[Sylvander]

"could a modem, for example, automatically be assigned a COM port, and it (the port being used) not show up under DM?"
Sorry to say, but I have no idea; I always have and still do find such things a bit mysterious. :confused:

[Whyzman]

COM ports are confusing... There are actually 4 COM ports, but only 2 can actually be used... http://www.pcguide.com/ts/x/comp/ioMultiple-c.html

[mjc]

If the machine has a built in modem, then it most definitely is assigned to COM 3.

And since it would most likely be a WinModem/software modem (most modem function handled by software as opposed to hardware) then, yes it is possible that Windows doesn't show it as a "COM" port...it may show the COM port under the modem properties.

Don't forget to check (under View in DM) to show 'Hidden devices'...

[FastLearner]

Thanks everyone. It was also nice to see that my hunch of it being a modem was probably right on target (even I guess right once in a while .:D).

I will instruct the individual to check out the modem properties and see what it says. I'm betting now that it reveals that it is assigned to Com 3. I'll let you all know.

Thanks again.

[mjc]

One of the things about COM ports is that there are no hard, fast rules connecting an assigned port to a physical connector...the connector can be assigned almost any 'port' number, if the OS allows it. Back in the days of DOS, ports were usually assigned 1 and 2 to the actual physical locations, in fact the could be jumpered that way and DOS would obey those assignments.

COM port assignments were both a curse and a blessing when Plug and Play was developed (at the time there was still a host of software that expected hard assignments...and some devices too....).

[FastLearner]

Yep, it's official. The gentleman has reported back that his modem properties (also in DM) reveal that hismodem is using Com port 3. I still can't figure out why it wouldn't be listed under "com ports" but that's a whole other problem indeed :D

Thanks to everyone for your commentary.

-FL

[mjc]

It isn't listed because it isn't a "real" COM port...it is a virtual port created and used by the modem drivers to allow other software that wants to use the modem know that it is supposed to act as if it were on COM 3.

Also, it is a sign that it is most definitely a 'softmodem' or 'Winmodem'.

[FastLearner]

so the interface between this modem and the motherboard is only "virtual" - seems like a very real and physical intzerface to me.

Why am I still having a hard time picturing this?

[saphalline]

Windows XP is based on the NT kernel with a whole lot of alteration! I've found that even on older hardware, COM ports are rarely set properly. The reason is that the OS itself is based almost entirely on P'n'P technology, so that the user can assign device properties independently of hardware connections. In fact, most BIOS-level port assignments off the ISA/Legacy bus are ignored most of the time. XP simply is not designed for such hardware, and getting any Parallel or Serial or ISA devices to function requires some extra steps. In fact, the only legacy functions that work properly every time in WinXP are the PS/2 ports. I'm not sure why that is.

To get the physical Serial port to show up in Device Manager as COM 1, you actually need to create it. I can't remember off-hand how to do this, but I remember having to do this in the past to get an external Serial modem to work with WinXP. I think you need to create it in the Control Panel or something. Do a search on M$'s website.

[jlreich]

seems like a very real and physical intzerface to me.

Why am I still having a hard time picturing this?

A COM port is not actually a port. It's an IRQ-I/O address assigned by the BIOS or OS set aside for communication devices. Whether that device is connected to a serial or parallel port. A COM "port" can be assigned to either a serial or a parallel port. Any real port (serial etc) can be assigned any one of the COM "ports", COM 1/2/3/4.

[mjc]

In a sense, all COM ports are virtual...just ports 1-4 used to have more or less 'standard' assignments. Also in pre-PnP days, you could not use ports 1 and 3 or 2 and 4 at the same time...they shared resources and when one was in use the other could not be used.

The physical interface doesn't really matter.

Confusing?

Yep. That is one of the things that taught me to approach all troubleshooting jobs with a large bottle of Tylenol on standby...

[jlreich]

Yep. That is one of the things that taught me to approach all troubleshooting jobs with a large bottle of Tylenol on standby...
Or with a shotgun! The gage of your choice. :p :D

[FastLearner]

Thanks guys. This is making some more sense now. My flaw was thinking about a com port as being a physical connection instead of just as a virtual assignment used by the device's drivers. While it may be true that most devices that use Com ports are in some way, shape or form connected to the motherboard, the ports are actually only addresses used for communications, as jlreich pointed out.

So here are two more related follow-up questions for you Tylenol addicts :D :

1) the 1-3 and 2-4 rule is no longer a consideration, correct?
2) how are the actual virtual com port numbers assigned - by the device drivers or by the OS when the device is installed (or none of the above)? The original problem of this thread leads me to believe that the device somehow assigns itself a virtual com port, but I'm not 100% sure

[jlreich]

1. Yes technically it still applies. But in a sense it doesn't. I mean how many of us are actually using our serial and parallel ports? Many mobo manufacturers are starting to lose these legacy ports altogether. I don't have a device that uses a serial or parallel port. Heck I don't even have a modem in my system. If anyone needs one I think I have five or six sitting in the basement. :p

2. If you have a plug and play BIOS, OS, and device it is assigned by the OS. There are default settings for many devices. But they can be changed if needed for some reason. But the chances of actually have such a conflict these days is very slim for reason stated above. If one the three mentioned above is not plug and play, then you would need to assign it manually (not going to happen these days).

[FastLearner]

You're definitely right about the availability of those ports becoming extinct, jlreich!

There is still some use for the ports, though, even with usb and other much faster interfaces being much more widely used. Where I work we manufacture (among tens of other types of products) devices used to act as a gateway between CAN and RS232 called a CANview, so we naturally still have a use for serial ports (our customers do, too...:)). We do not buy laptops that don't have at least one serial port, which are getting harder and harder to find.

There are still a couple of Samsungs out there and my personal choice, the Fujitsu-Siemens Lifebook E series, which still luckily have an RS232 port.

[saphalline]

Serial and parallel ports are indeed used by many industrial and old DOS-style apps. I don't get a lot of requests for those old ports, but those that do request them are quite adamant! :p

I understand that these ports are still useful for some things, but these things are often niche-products these days. I don't see how people can still expect consumer products (which move to new technologies before they're even out yet!) to cater to their 1990's needs. If you do have a need for those old ports still, you'll need to find another hardware vendor. Off-the-shelf products intended for the latest buzzwords like "ViiV" are not going to support you!