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AST RESEARCH, INC.              TECHNICAL BULLETIN # 0949       7-19-94

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   WINDOWS FOR WORKGROUPS AND PENTIUM(TM)-BASED SYSTEMS WITH A 16550 UART CHIP


PROBLEM:        When using Windows for Workgroups version 3.11 with serial
                communications software, the following problems may occur:

                1- Using a Pentium(TM)-based machine with a 16550 UART chip,
                   when the serial communications application attempts to open
                   the communications port, the system may stop responding
                   (hangs) if there is data in the chip.

                2- When using communications software, one connection may be
                   possible after starting Windows for Workgroups, but any
                   subsequent connections may fail and may hang the system.
                   While this does not normally cause problems, the second
                   connection may fail with some modems.

CAUSE:          1- A problem with the 16550 UART implementation causes the chip
                   to become trapped in a mode in which data is always
                   detected in its FIFO buffer.

                2- This problem occurs when SERIAL.386 sends an extra NUL
                   character through the port, when the communications
                   software calls the CloseComm Application Program Interface
                   (API) function.

SYSTEMS
AFFECTED:       All Pentium(TM)-based systems with a 16550 UART chip.

SOLUTION:       Download the <A HREF="ftp://ftp.ast.com/MISC/SERIAL.EXE">SERIAL.EXE</A> file from AST’s BBS and copy it onto a
                diskette.  This WG1001 file contains an updated SERIAL.386
                driver that corrects both problems.

                To install the updated SERIAL.386 file do the following:

                1. Quit Windows for Workgroups.

                2. Make a backup copy of the currently installed SERIAL.386
                   file by typing the following at the MS-DOS command prompt
                   and then pressing <ENTER>:

                           ren <drive>:<path>\serial.386 serial.old

                   where <drive>:<path> is the location of your Windows SYSTEM
                   subdirectory.

                   For example, if your Windows directory is called WINDOWS and
                   it is on drive C, type the following at the MS-DOS command
                   prompt and then press <ENTER>:

                           ren c:\windows\system\serial.386 serial.old

                3. Insert the WG1001 file in the appropriate floppy disk drive.

                4. To copy the file to the Windows SYSTEM subdirectory, type
                   the following at the MS-DOS command prompt and then press
                   <ENTER>:

                           copy <drive>:\serial.386 <destination>:

                   where <drive> is the floppy disk drive containing the WG1001
                   file and <destination> is the drive and directory of your
                   Windows SYSTEM subdirectory.

                   For example, if the WG1001 file is in drive A and your
                   Windows directory is called WINDOWS, and it is on drive C,
                   type the following at the MS-DOS command prompt and then
                   press ENTER:

                           copy a:\serial.386 c:\windows\system