Reassign PCI COM port?

Dennis Faas's picture

Infopackets Reader Ric J. writes:

" Hi Dennis,

I recently tried to install a new PCI modem card in my system. The modem is Plug and Play (PNP) and should automatically configure itself once the drivers are installed. Unfortunately, the modem won't properly install on my machine. I went into Device Manager and found that the modem assigned itself to COM1, which was already in use. So my question is: how do I change the COM port so that the modem won't conflict with COM1? "

Side note: PCI stands for Peripheral Component Interconnect, or 'personal computer bus'. A COM port is short form for "communication port" and is a pathway set aside for modems or legacy serial mice (mouse). IRQs (interrupt request, noted below) are used in conjunction with COM ports and typically cannot be shared with more than one device.

My response:

Unfortunately, Windows Device Manager doesn't always allow the user to assign COM ports, DMAs, or IRQs haphazardly. It's a pain in the neck when Plug and Play hardware won't assign itself to the proper communication channel, but there almost always another way to resolve this problem. What I am about to suggest may not be the most correct approach, but it should set you on the right track:

  1. Go to your Control Panel -> Modems, click your modem properties, and see if there is a way to assign a new COM port to your modem.
  2. If that doesn't work, go to Device Manager and delete COM1 from the "Ports (COM & LPT)" tab. Restart your computer, press DEL / F2 to enter your Setup, and disable COM1 in your BIOS. Reboot the computer. Windows should recognize that COM1 is no longer assigned through your BIOS and should assign the modem to COM1 without any conflict.
  3. If that doesn't work, try plugging the modem into another PCI slot. Sometimes this will force the modem to acquire another IRQ / COM port.
  4. If that doesn't work, look at your modem manual and see if there is a hardware setting on the modem itself that will allow you to change the COM port / IRQ setting for the modem. Some 3Com / US Robotics (PCI) modems have this setting.

Good luck!

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