Path: utzoo!attcan!uunet!ncrlnk!ncrcae!hubcap!gatech!bloom-beacon!ATHENA.MIT.EDU!swick
From: swick@ATHENA.MIT.EDU (Ralph R. Swick)
Newsgroups: comp.windows.x
Subject: Re: ASCII terminals vs. X Window System terminals
Message-ID: <8901181314.AA12697@LYRE.MIT.EDU>
Date: 18 Jan 89 13:14:51 GMT
References: <8901172105.AA06900@hydra>
Sender: daemon@bloom-beacon.MIT.EDU
Organization: DEC/MIT Project Athena
Lines: 17

>Can anyone with experience in replacing ASCII terminals with X Window
>System terminals (e.g., Visual 640 XDS) comment on the difference in
>CPU cycles required to support ASCII vs. X Window System.  Suppose I
>have a VAX supporting twenty users - how much extra overhead is
>imposed by talking X instead of async. serial?

I think the differences in overhead between driving the X protocol
on top of (e.g. TCP) on top of IP and bare-bones ASCII with XON/XOFF,
various line disciplines, etc. (on e.g. RS422) will be far outweighed
by the effect of just a couple of moderately sophisticated users
of (any) window system.  It would be appropriate to think of an ASCII
terminal as a governor (constrictor) on each user.  The two environments
and the kinds of things users try to do with each are so vastly
different that capacity planning based upon system overhead metrics
is not likely to get very far.

I suggest you arrange a visit here to Project Athena. :-)