7300 and 9600 baud modems

[Albert Hybl Dept of Biophysics SM]

In message: <581 at limbic.UUCP> from gil at limbic.UUCP, Gil Kloepfer Jr.
writes:
>A problem I *have* noticed is calling at Trailblazer speed to a system
>from my VT100 *through* the UNIX-pc results in many lost characters
>on my receiving end.  I'm not sure whether this is due to the 3B1 not
>being able to handle 2 serial ports at high-speed, or the VT100 being
>too slow and causing too many characters to be queued-up at the device
>driver level.  In any event, forcing the Telebit speed to 9600 baud
>doesn't fix the problem.  | Gil Kloepfer, Jr.

I have a similar problem when communicating through an intermediate
host.  While attempting to isolate the problem, I did the
following:  first, from machine hybl (a 3B1 with the old uucp), I
"cu -l/dev/ph1 328xxxx" to machine unix65 (a unix-pc 7300 with HDB);
second, from unix65, I "cu mbph | tee cu.mbph" over a direct connection
at 9600 baud using the tty000 port (mbph is a 3B2 with HDB); third,
I did a few "ls -CF" operations to demonstrate dropped characters.
The characters that were obviously missing from the output displayed
on the monitor of machine hybl were also missing from file cu.mbph.
This suggests that the intermediate host is not able to properly
control the flow of characters from mbph.    Why?

If I login directly to machine mbph from either machine unix65 or hybl,
I can "cd /" then "ls -sailFR" and watch the output scroll faultlessly
by on the monitor.  A portion from file cu.mbph follows: (I have
added some annotation to the file.)

> $ ls -CF
> Configure*     README         filexp*        patch.c        util.h
> EXTERN.h       all            inp.c          patch.man      version.c
> INTERh       common.h       inp.h          patchlevel.h   version.h
      ^^ Two characters lost from here
> MANIFEST       config.H       message        pch.c
> Makefile       config.h       myread         pch.h
> Makefile.SH    config.sh      patch*         util.c

> $ ls -CF
> Configure*     README         filexp*        patch.c        util.h
> EXTERN.h       all            inp.c          patch.man      version.c
> INTERh       common.h       inp.h          patchlevel.h   version.h
      ^^ It is reproducible
> MANIFEST       config.H       message        pch.c
> Makefile       config.h       myread         pch.h
> Makefile.SH    config.sh      patch*         util.c

> $ ls -CF I*
> INTERN.h
       ^^    These are the lost characters.

Thanks,
----------------------------------------------------------------------
Albert Hybl, PhD.              Office UUCP: uunet!mimsy!mbph!hybl
Department of Biophysics       Home   UUCP: uunet!mimsy!mbph!hybl!ah
University of Maryland                CoSy: ahybl
School of Medicine             Office Phone: (301) 328-7940
Baltimore, MD  21201           Home   Phone: (301) 243-1710
----------------------------------------------------------------------
Responders--DO NOT USE:  hybl at cs.umd.edu  or  ah at cs.umd.edu