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Standard Serial Ports (COM1 and COM2) Cannot be Installed

    Question

  • I need to use both of the standard RS-232 COM ports for some instrumentation I use.  Under Windows 7 RC, the COM ports are not installed during windows installation.  If I try to add them with the Legacy installation option, the resources are already bound to other devices (PCI Bus for IO and ACPI for IRQ).  No unused IO and IRQ are available.
    Any suggestions?
    Wednesday, September 2, 2009 2:14 PM

Answers

  • The issue can be caused due to some devices have used the IRQs which COM1 and COM2 are supposed to use. COM1 uses IRT4 and COM2 uses IRT3.

     

    I suggest you can first check it in System Information.

     

    1. Click Start, type System Information in the Search box.

    2. Click Hardware Resources, go to IRQ.

     

    Then, you can see the devices which are using IRT4 and IRT3.

     

    After that, you can refer to the following support articles to change the IRQ settings.

     

    Changing IRQ Settings

    http://www.helpwithpcs.com/upgrading/change-irq-settings.htm

     

    Resolving IRQ/COM port conflicts

    http://service1.symantec.com/SUPPORT/pca.nsf/docid/1996112511055

     

    Note: The steps are not for Win 7 directly, meanwhile, they are similar, just for your reference.

     

    Also, after the changing, the devices which original using IRT4 and IRT3 may not work. Please be careful.

     

    Good luck!

    Friday, September 4, 2009 10:00 AM
  • First of all you may verify if COM1 and COM2 is actually installed. To do so, open Device Manager, expand the Ports branch.

    If the ports are not listed, it can be hardware compatibility issue. You may need to install additional COM drivers from the motherboard manufacturer.

    If the two ports are present, please check if the ports are occupied. The website “Changing IRQ Settings” in Nina’s post can help you on this.

    If the issue occurs when the ports are not occupied, and the suggestions on these posts do not work, I suspect that your instrumentations cannot work on the COM ports with Windows 7 COM ports driver.


    Arthur Xie - MSFT
    Thursday, September 10, 2009 9:22 AM
    Moderator

All replies

  • The issue can be caused due to some devices have used the IRQs which COM1 and COM2 are supposed to use. COM1 uses IRT4 and COM2 uses IRT3.

     

    I suggest you can first check it in System Information.

     

    1. Click Start, type System Information in the Search box.

    2. Click Hardware Resources, go to IRQ.

     

    Then, you can see the devices which are using IRT4 and IRT3.

     

    After that, you can refer to the following support articles to change the IRQ settings.

     

    Changing IRQ Settings

    http://www.helpwithpcs.com/upgrading/change-irq-settings.htm

     

    Resolving IRQ/COM port conflicts

    http://service1.symantec.com/SUPPORT/pca.nsf/docid/1996112511055

     

    Note: The steps are not for Win 7 directly, meanwhile, they are similar, just for your reference.

     

    Also, after the changing, the devices which original using IRT4 and IRT3 may not work. Please be careful.

     

    Good luck!

    Friday, September 4, 2009 10:00 AM
  • First of all you may verify if COM1 and COM2 is actually installed. To do so, open Device Manager, expand the Ports branch.

    If the ports are not listed, it can be hardware compatibility issue. You may need to install additional COM drivers from the motherboard manufacturer.

    If the two ports are present, please check if the ports are occupied. The website “Changing IRQ Settings” in Nina’s post can help you on this.

    If the issue occurs when the ports are not occupied, and the suggestions on these posts do not work, I suspect that your instrumentations cannot work on the COM ports with Windows 7 COM ports driver.


    Arthur Xie - MSFT
    Thursday, September 10, 2009 9:22 AM
    Moderator