🚀 go-pugleaf

A common cause of this problem is a 16550-compatible chip that isn't
fully compatible. Typically this is seen on Pentium systems with serial
ports integrated on the motherboard, but it can also happen with add-on
cards, particularly "multi-I/O" cards based on popular SMC chips.
<http://www.microsoft.com/Support/KBSL/DEVELOPR/win_dk/Q119853.htm>

   * Updated drivers are available from SMC and Microsoft to work around
     the problem. The SMC package
     <ftp://ftp.smc.com/pub/chips/superio/serial.zip> includes both SMC's
     updated COMM.DRV for regular Windows 3.1 and Microsoft's updated
     SERIAL.386 for Windows for Workgroups 3.11; the Microsoft package
     <ftp://ftp.microsoft.com/Softlib/MSLFILES/WG1001.EXE> includes only
     Microsoft's updated SERIAL.386 (10,620 bytes dated 2/17/94). But see
     warning below.
   * Alternatively you should be able to completely solve (or simply test)
     the problem by turning off the UART buffers. To do that, put the
     following in the [386Enh] section of your SYSTEM.INI file:
     COMnFIFO=0
     where n is the number of your modem COM port (e.g., COM2FIFO=0). The
     drawback is that you then won't get the benefit of the 16550 FIFO
     buffers.

Warning: Although Microsoft specifically identifies the SMC '665 chip as
the problem, the author has personally verified that a problem also exists
in the SMC '666 chip (FDC37C666GT). Furthermore, although the original FIFO
problem is reportedly fixed in current chip production, the author has
personally verified that a problem (perhaps a different problem) still
exists as of August 1995. The author has also personally verified that:

   * SMC's updated COMM.DRV does not correct this current problem; and
   * Microsoft's updated SERIAL.386 is not fully satisfactory: lockups are
     very rare but not entirely eliminated, and Windows multitasking is
     adversely affected during certain communications operations (e.g.,
     negotiating a dialup PPP link with Trumpet Winsock 2.1F).

The only fully effective workaround is to disable the FIFO buffers (as
described above). For this reason the author does not currently recommend
products that use SMC "multi-I/O" chips.

--
Best regards,
John   mailto:JNavas@NavasGrp.com     http://web.aimnet.com/~jnavas/
       28800 Modem FAQ: http://web.aimnet.com/~jnavas/modem/faq.html