MK> For what I have experience with -- generic BBS stuff -- secondary com
 MK> threads are generally a waste of CPU.  However, I can envision situations

Just because a thread exists does not mean it is using more CPU.

A secondary thread,  with the proper read mode
(wait-for-something),allows you to miminimize the number of DosRead's you
have to do,  thus saving _loads_ of CPU.   A well written two-thread read
model will be faster and more efficient than a one thread model;similarly
for writes if you are doing lots of small ones.

It also :

    - allows a much larger buffer than the puny one in com.sys,
    - better lends itself to having a data-driven design in your program.
    - "does nothing" better.

--- Maximus/2 2.02p1