COM ports

By default, the PC design allows for a maximum of 4 serial ports: COM1..COM4
De standard is that COM1 and COM3 share the same interrupt and so do COM2 and COM4. Windows 95/98/ME allows this, but Windows NT/2000 does not, so if you run Win2K, you'll have to assign unique IRQ's to COM3 and COM4 manually for it to work under NT/2000.

But besides this, you always have the option of adding a serial adapter who uses PCI version 2.1 or higher. Using this method you can add up to 128 serial ports (theoretically) since they will all use the same IRQ. However, most DOS software will not be able to access these ports, only Windows software does.

In short: Up to 4 COM ports, no problem. Above that, you need to use a few tricks, but it can be done.

Hope you don't mind me breaking in here but I've had no luck at all in installing a PCI single serial port card in my Dimension 4100. It's recognised OK a COM2 in Device Manager but it refuses to send anything out to the outside world. No conflicts reported anywhere. No freezes-it just quietly sits there doing nothing .

>In short: Up to 4 COM ports, no problem. Above that, you need to use a few tricks, but it can be done.<

If you could suggest a trick or two to get my extra port going I'd be much obliged to you.

Maurice (UK)

You have to make sure you assign the right I/O base address and IRQ to the COM port.

You say you have a 4100 so you have one serial port already installed (COM1), so the port you're adding will be COM2.
COM2 should be setup using I/O base address 02F8 and IRQ 3.
You should check this in the Windows device manager in the "Resources" tab. If you see a different I/O address or a different IRQ you should check the manual that came with the serial port card on how to change it. (It may also work if you change it directly in the "Resources" tab settings. Just try.)

--/--

You wanted "tricks"? :)

To find out if your system detected the serial port properly during POST, do this:

Open a DOS box, type DEBUG and press Enter.
You should see a hyphen "-" indicating debug is ready.
Now type
- D40:0
and press Enter
You should see 128 bytes of the BIOS parameter table. What you're interrested in is the first line. In your case, with 2 serial ports it should read:

0040:0000 F8 03 F8 02 00 00 00 00 (and then some more)

If you see this, you're ok. The F8 03 and F8 02 are your COM1 and COM2 respectively (eg. 03F8 and 02F8 in intel reverse notation). If you see F8 03 00 00, this indicates that your PC did not recognise the second COM port. If you see anything else then F8 02 as the second pair of bytes, than the system did see the COM port, but has assigned it the wrong I/O address.

To exit debug type Q and press Enter.

PS. This last information is only relevant if you want to access the second COM port from DOS. If you're only going to use the port from within Windows you can skip this part.




Message Edited on 08/18/01 12:10AM by Kamikaasje

Thanks for the gen and the tricks. That gives me something to check on.

If I have any significant results I'll come back to you.

M.

Have checked on all that you told me.

Device Manager: COM2 No conflicts, IRQ3, I/O 02F8-02FF

DOS DEBUG: Presents exactly as your example.

Additional: Norton Diagnostics (from Windows) Shows COM1 OK and passes all tests, but does not see COM2.

(For what it might be worth, Norton shows on it's Memory Test "Error detected at 257810432") but I don't suppose this is relevant).

Still my COM2 sits there doing nothing. It won't communicate with anything I connect to it. This is the third card of this type that I've installed, all with the same results.

A suggestion from elsewhere is to do the dance of the PCI slots. Would you think that this is the only thing left to me? As all the slots are currently occupied this may take some time to cover all the possible combinations but I'm happy to have a go.

Thanks for your help.

M.

No, swapping the card to a different PCI slot would not help you in this case unless the PCI slot itself was broken. The reason why swapping cards between PCI slots is sometimes suggested as a possible solution has to do with the automatic assignment of IRQ's (and I/O base addresses depending on the type of PC card). Normally PCI cards are assigned their IRQ by the BIOS or by the operating system (eg. Plug-n-Pray). The assignment is linked to the PCI slot number, so swapping the card to a different slot can force the system to assign it a different IRQ which sometimes can solve a problem in case it is caused by a conflict in resources. However, in your case the IRQ is fixed (IRQ=3) so swapping is not a solution.

In order for me to help you any further, could you please provide me with the details of your serial PCI card, eg. manufacturer and exact model number.
And also how do you detect that the port is not transmitting or receiving. You must have attached something to the other end of the serial cable. A modem perhaps or some other device?
What version of Windows are you running?

A few more suggestions:
- Did you check the cable?
- Are you sure it's the right type of cable (cross vs. straight-thru)?
- Can you try a different device to check communications?
And other things like that.


PS. I wouldn't worry about the memory error that Norton Diagnostics report. It's exactly at the 256MB boundry, and it is a know bug in Norton Diagnostics.


Message Edited on 08/18/01 03:04PM by kamikaasje

Maurice: If DOS recognizes it and Windows recognizes (don’t care what Norton says) the problem is that your software is not communicating with it.

Unless Kamikaasje has something better, as well he could! I suggest moving the device you currently have on com1 to the com2 port and see it works there. If it does, leave it there and install whatever your new device on com1.

By the way, did Bill Parker get his Sharp up and running???

Hello Jim, thanks for your reply.

>If DOS recognizes it and Windows recognizes (don’t care what Norton says) the problem is that your software is not communicating with it.<

Point taken.

>Unless Kamikaasje has something better, as well he could! I suggest moving the device you currently have on com1 to the com2 port and see it works there. If it does, leave it there and install whatever your new device on com1.<

K. has sent me a reply which I'm still working on. I have swapped the external devices with exactly the same results. My external modem on COM1 which works OK there won't respond when I swap it to COM2 (I did chang it's port allocation in DUN). COM2 is still dead and quiet.

>By the way, did Bill Parker get his Sharp up and running??<

I don't know. I didn't intend to take over his thread. I expect he will respond in due course.

M.

Thanks for throwing me a lifeline on this, kamikaasje.

>In order to help you any further.........<

Serial card: Single-port Intek21 PCI IO 1S-650 Board (am on my third such card)
Supplier: Microcomputer Research(UK) Ltd. www.mri.co.uk
Driver kit: Latest download from their Web site.
Windows98SE
Dimension 4100

I have connected my Home Automation X10 to COM2 but without getting transmission to the Controller Interface unit. I have checked it's COM cable because the X10 works OK from COM1.

I changed my external modem from it's usual place on COM1 where it works OK to COM2 and it then won't respond (I did reset it's comport allocation in DUN).

You may ask if I've contacted the card's supplier over this problem....

Yes, I have had several talks with them but they can't suggest anything more that I've done and described to you already.

Thanks for the comment on Norton Diagnostics.

I think you will see from the above information that I've done several checks to try to pinpoint the trouble, and assuming I've not done something completey daft this seems to be a difficult and frustating one. All other PCI stuff I've added has worked first time.

Hope you can help.

M.

I'm having a hard time finding info on the card on the web. It seems Intek21 is no longer in business or it's PCI card division has been bought (presumably by SIIG).

Could you check for me if there are any jumpers on the card? Especially if there is one labled DTE or DSE ?

Apologies for the dealy.

>Could you check for me if there are any jumpers on the card? Especially if there is one labled DTE or DSE ?<

No jumpers there. That seems not to leave many options.

Maurice