Microsoft KB Archive/100372

= Detecting Windows NT serial ports =

Article ID: 100372

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT Advanced Server 3.1
 * Microsoft Windows NT Workstation 3.1
 * Microsoft Windows NT Advanced Server 3.1
 * Microsoft Windows NT Workstation 3.5
 * Microsoft Windows NT Workstation 3.51
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Server 3.5
 * Microsoft Windows NT Server 3.51
 * Microsoft Windows NT Server 4.0 Standard Edition

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This article was previously published under Q100372



SUMMARY
Windows NT manages serial (COM) ports somewhat differently from the way Windows 3.1 does. In Windows 3.1, you can observe and configure all the COM ports from Ports in Control Panel. In Windows NT, only unused COM ports are displayed in Control Panel. For example, if a mouse is connected to COM1, COM1 is not available in Control Panel, nor is it listed. To check a COM port and perform any trouble-shooting steps, you need to use Registry Editor.

Finding Serial Ports in Registry Editor
To determine what is using a COM port, from Registry Editor go to the following subkey:

\HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System \MultifunctionAdapter\0\SerialController\...

Note If you have an EISA type computer, MultifunctionAdapter will be EisaAdapter.

Each COM port is stored in one of the numbered subkeys. If you have two COM ports, COM1 and COM2, you would find them stored under 0 and 1, respectively.

If a mouse is using a COM port, you will find a PointerPeripheral subkey under the serial ports subkey. For example: If you have a mouse on COM1, you would see the following:

...\SerialController\0\PointerPeripheral

If PointerPeripheral is absent, then the serial port is in use by some other device.

Additional Differences in Windows NT Control Panel
You might notice an additional difference in Windows NT Control Panel. If you select a COM port, choose Settings, and then choose Advanced, the following message may be displayed in a dialog box:

There are no user configurable Advanced I/O parameters for this COM port.

This means that Windows NT has obtained all the information it needs for the port from NTDETECT.COM (or OSLOADER.EXE on RISC-based computers). This ensures that redundant or incorrect information is not entered.

Additional query words: prodnt

Keywords: kbhardware KB100372

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