Serial port set to not used in CMOS after restarting in MS-DOS mode.

Document ID: 94000616

Posted Date: 1996-08-19

Last Updated: 1996-08-19

Distribution: View Public Website

Applicable Models

Portege 7000CT

Portege 7010CT

Tecra 8000

Issue: Describes a registry editing procedure to solve this issue.
Procedure: WARNING: The procedure you are about to follow to fix your stated problem involves editing the system Registry files. Using Registry Editor incorrectly can cause serious problems which may cause the loss of data, and may require you to reinstall Windows 95. Neither Toshiba nor Microsoft will guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the Changing Keys And Values online Help topic in Registry Editor (Regedit.exe). Note that you should make a backup copy of the registry files before you edit the registry.

To create an icon on your desktop that will restore the registry to the most recently saved version, do the following:

1. Go to the Start Menu / Run command
2. Type "regedit /e restore.reg" (where restore can be any filename)

Double-clicking on the desktop icon will restore the registry.

Issue:
After selecting Start/Shutdown/Restart the computer in MS-DOS mode, serial devices that were functioning, under the Windows 98 graphical interface, no longer do even though the DOS driver appears to be loading correctly. The issue typically gets reported when a user tries to use a serial mouse after restarting system in MS-DOS mode. Upon going into CMOS, using the TSETUP utility, the serial port is set to not used.

Resolution:
The problem is caused by the Windows 98 power management subsystem deactivating the serial port, when restarting in MS-DOS mode, and a DOS based driver's inability to "wake or reactivate" the serial port. The issue only occurs on systems that have an ACPI BIOS and Windows ''98. To work around this issue, make the following registry modification.

WARNING: Using the Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Toshiba cannot guarantee that problems resulting from the incorrect use of the Registry Editor can be solved. Use the Registry Editor at your own risk.
For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

NOTE: You should back up the registry before you edit it.

1. Boot into Windows 98.

2. Go to the "START" menu, click on "RUN".

3. Enter "REGEDIT.EXE" and click on "OK" to continue.

4. Go to the following registry key:

"Hkey_Local_Machine\System\CurrentControlSet\Services\VxD\VCOMM"

5. Change the value of the "EnablePowerManagement" key from "01 00 00 00" to "00 00 00 00".
6. Exit registry and restart system.

By making this change, the computer's COM port power management is disabled.
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