Pentium-Based Machine Hangs with Communication Applications

• Microsoft Windows operating system versions 3.1, 3.11
• Microsoft Windows for Workgroups versions 3.1, 3.11

SYMPTOMS

Pentium-based machines with a peripheral component interface (PCI) bus and a 16550 UART chip stop responding (hang) or exhibit other unexpected behavior when you use communication applications, such as Microsoft At Work PC Fax or Microsoft Terminal.

In some cases, you may be able to run the software successfully once but then experience problems when you try to run it a second time (before Windows is restarted).

CAUSE

The PCI bus uses a new universal asynchronous receiver transmitter (UART) chip that identifies itself as a 16550 chip but does not handle the 16-bit buffer the same way that the 16550 UART chip does.

These problems occur if there is data in the chip when the serial communications application attempts to open the communications port. A problem with the chip implementation causes the chip to become trapped in a mode in which data is always detected in its FIFO buffer.

RESOLUTION

To correct this problem under Windows for Workgroups 3.11, obtain the updated SERIAL.386 file included with PSS Application Note WG1001: Updated SERIAL.386 Driver for Windows for Workgroups.

For more information about WG1001, query on the following words in the Microsoft Knowledge Base:

   wg1001 and appnote