That didn't work in Win 3.1; neither did anything else based on an assumption
of inadequate buffering. Turns out the problem was that I had my modem on COM4,
and nothing on COM1-3. Windows doesn't like that - seems it wants the COM ports
used in the order they are numbered. Switching the modem to COM1 cured the
problem.
The source of the info that put me straight? It wasn't Microsoft - even though
I have their Resource Kit and attended one of their technical workshops. The
credit goes to Brian Livingston, in "Windows 3.1 Secrets" (many of which also
apply to Windows 3.0).
Why do I have to rely on third-party material for something like that? Or is
this the result of a peculiarity in the modem (a Supra 2400i) or Telix SE that
Microsoft pretends not to know about?