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  1. #1
    New Lounger
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    I recently received an old Dell Optiplex 320 which had been used in an office environment on an LAN and had no internal modem. I got a CONEXANT D850 from Dell and installed it and the driver. It functioned properly for about two months then suddenly kicked me off-line in mid-session. When I tried to restart the dialer said it couldn't find the modem so I ran the Dell Modem Helper diagnostics and it said the modem was functioning but the COM3 port was in use by another device. I checked the Device Manager couldn't find any conflicts but only two Com ports (1 and 2) are listed along with the LPT1printer port. Both Device Manager and the Dell diagnostics say the modem is functional.
    Any advice on how I go about finding and clearing the conflict will be appreciated.

  2. #2
    Super Moderator Deadeye81's Avatar
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    Hi Phil, and welcome to the Lounge!

    What operating system are you using? Does the Optiplex 320 have the Ethernet capability built into the motherboard, or is is an add-on card like your CONEXANT D850 modem? If Ethernet is built in, go into the BIOS to disable it. If it is an add-on card, remove it from your computer. Since you do not use Ethernet on this 320, there is little reason to allow Ethernet to consume your resources.

    A common cause of Com port conflicts is two devices assigned to Com 1 and Com 3. Both of these Com ports use the same hardware interrupt (IRQ 4), while Com 2 and Com 4 share IRQ 3. Is there any new hardware that has been added to your system just before the conflict was reported? Or was a driver installed just before your connections stopped. If so, that driver may be addressing the same IRQ as the modem. Also, check your BIOS to see if it will reveal what Com ports have been assigned to devices.

    A useful tool to see everything in your computer is System Information for Windows (SIW) available here for free. You can run this program, look under Hardware>Resources>IRQ to see all the interrupts assigned on your computer. Look particularly for IRQ4 and IRQ3 to see what is using those.

    Hope this helps.
    Deadeye81

    "We make a living by what we get, we make a life by what we give." Sir Winston Churchill

  3. #3
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    Hi Gerald, thanks for the welcome and the quick reply.
    The OptiPlex is running Windows XP Pro SP3. I did find a network card, which I removed, and I disabled the Ethernet Controller in Device Manager. I noticed that Device Manager has dropped the COM2 port but still has COM1 and LPT1. The Modem is still using COM3.
    I ran the SIW software and see that the Modem is assigned IRQ22 and COM1 is assigned IRQ4. No listings for IRQ's 1, 2 or 3. IRQ22 is shared with the ATI SATA Controller. Is there some way I can force the Modem to use another interupt and avoid conflicts?

  4. #4
    Super Moderator Deadeye81's Avatar
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    Phil,

    Some BIOS's will identify which card slots on the motherboard share an interrupt with an on board device. If you BIOS does that, then look for something like "PnP/PCI Configuration", or "IRQ Resources", or "PCI IRQ Assignment". If you have a manual for your motherboard, check it. If you don't have a manual for the board, you might be able to download a manual.pdf from Dell, or from the motherboard manufacturer's site. This can help you pick a card slot that should not contribute to conflicts.

    If the above results in a dead end, since the card slot your Modem occupies and the built in SATA controller are sharing the same interupt, IRQ22, then find an empty PCI slot on your motherboard, and remove your Modem from its present location to that PCI slot. If you have another one or two slots open, that is even better. Hopefully, moving to another slot will resolve the conflict your Modem is having with the SATA controller.
    Deadeye81

    "We make a living by what we get, we make a life by what we give." Sir Winston Churchill

  5. #5
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    Gerald,
    I opened the BIOS and it is pretty bare bones. I don't see anything that looks like communications altering settings. I also moved the Modem card to the only other PCI slot and this resulted in a change from IRQ22 to IRQ21, which is also marked as shared although it doesn't show which device is doing the sharing. Also the COM3 changed to COM4. However, since the computer can't even find the modem now I don't know if there is a port conflict or not. Looks like my bargin computer (it was free) is pretty much worth what I paid for it. Anyhow, it still runs faster than my old COMPAC so I can use it for jobs that don't require the internet.
    Thanks for your help.

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