Win16 Subsystem Fails When Used with Equinox Serial Driver (126429)

SYMPTOMS

When using Equinox Systems intelligent serial board and driver, the Win16 subsystem fails when a 16-bit terminal application is run. Example programs of this type are WinCim and Procomm Plus for Windows.

The following message may appear:

Application caused an exception in the Win16 subsystem

Then, the 16-bit application and the Win16 subsystem terminate. However, Windows NT does not fail.

CAUSE

The Win16 subsystem is not correctly dealing with overlapped reads when communicating with the COM ports.

When a ReadFile is issued, the Win16 subsystem assumes it either has completed immediately or that it has failed (that is, it assumes that the read is synchronous). When using the Equinox serial driver, the Win16 subsystem assumes all the reads are failing because none of the reads are completed immediately. This situation eventually causes the Win16 subsystem to fail.

STATUS

Microsoft has confirmed this to be a problem in Windows NT Workstation and Windows NT Server version 3.5. This problem was corrected in the latest U.S. Service Pack for Windows NT version 3.5. For information on obtaining the Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

   S E R V P A C K

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