Microsoft KB Archive/82407

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Vistacom Problems When Switching COM Ports

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Q82407

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The information in this article applies to:


 * Microsoft Windows versions 3.0, 3.0a, 3.1, 3.11

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SUMMARY
Under Microsoft Windows, Vistacom and its associated terminate-and-stay- resident (TSR) program, DEVLOAD.EXE, can cause interrupt request line (IRQ) conflicts when running in 386 enhanced mode.

Disabling the Combuff device in the Windows SYSTEM.INI file corrects this problem.

MORE INFORMATION
Vistacom is a terminal emulator manufactured by Control Data. Vistacom can cause interrupt conflicts when you disconnect from a COM port and then try to use another COM port on the same IRQ while running in a Windows virtual machine. For example, disconnect from COM3 and then try to use COM1. Under the standard IBM serial port configuration, COM1 and COM3 use the same interrupt (IRQ 4).

To correct this problem, disable the Combuff device in the Windows SYSTEM.INI file. In the [386enh] section of the SYSTEM.INI, either set the line &quot;COMxBuffer=0&quot; (where &quot;x&quot; is the COM port number) or remove the line &quot;device=*combuff&quot;.

Vistacom is manufactured by a vendor independent of Microsoft; we make no warranty, implied or otherwise, regarding this product's performance or reliability.

Additional query words: 3.10 3.1 3.11

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Issue type :

Technology : kbWin3xSearch kbWin300 kbWin300a kbWin310 kbWin311