Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!think!snorkelwacker!apple!vsi1!lmb
From: lmb@vicom.com (Larry Blair)
Newsgroups: comp.realtime
Subject: Re: What is "real-time" really?
Message-ID: <1990Feb23.191100.18448@vicom.com>
Date: 23 Feb 90 19:11:00 GMT
References: <98692@linus.UUCP>
Organization: Vicom Systems Inc., Fremont, CA
Lines: 21

In article <98692@linus.UUCP> duncant@mbunix.mitre.org (Thomson) writes:
=
=
=Someone asked me recently what real-time really means.  After some thought,
=I answered that real-time systems were simply those {in which the 
=timing constraints were so tight that speciall programming techniques
=were required.  Under this definition, a "real-time" system of today may
=become a non-real-time system whan hardware gets fast enough that I can 
=program it using any regular old operating system (say plain old UNIX)
=using high level language (no assembly language optimization) and not have
=to worry about my software failing to meet its deadlines.
=~rk
=Anyone care to comment?  What is the best definition of real-time?

One can say that realtime means running fast enough to meet your time
constraints, but to me there are two things that all realtime systems
share: determinism and low latency.  UNIX is definitely not deterministic
and the only way to get low latency is to put time critical code in the intr
routine.
-- 
Larry Blair   ames!vsi1!lmb   lmb@vicom.com