Path: utzoo!utgpu!jarvis.csri.toronto.edu!me!kokody2
Newsgroups: comp.realtime
From: kokody2@me.utoronto.ca (Gerry Kokodyniak)
Subject: Re: Realtime Unix?
Message-ID: <1990Feb28.163109.17440@me.toronto.edu>
Followup-To: comp.realtime
Keywords: time critical applications
Reply-To: kokody2@hammer.me.UUCP (Gerry Kokodyniak)
Organization: University of Toronto, Department of Mechanical Engineering
References: <2057@hydra.riacs.edu>
Date: 28 Feb 90 21:31:09 GMT


Phil Klimbal (klimbal@riacs.edu) in <2057@hydra.riacs.edu> writes:
> Many of the "Realtime Unix" systems provide what I would 
> characterize as "soft realtime" performance (lets say 1 
> millisecond dispatch latency).  What would I do with such 
> a system?  How many people actually want all the functionality
> of a complete Unix system for their time critical applications?
> 
> --Phil Klimbal
>   klimbal@riacs.edu

Realtime Unix becomes very useful in data acquisition/control environments.
An example is say one wants to control several aspects of an experiment and
take data at the same time. In an MSDOS environment one would have to
integrate the different pid loops, data acquisition, etc etc into one
program and one would have to integrate hardware to handle such things as
function generation. If one wanted to add or subtract control/data acquisition
modules, the timing of the program would be seriously affected and one would 
have to rework the program to optimize to the desired timing. On a real-time
unix system one could have a child process that is a function generator,
another child process acquiring data, another child process controlling
one parameter etc etc. With the addition/subtraction of a process, the
timing aspects remain the same. One also has the advantages of the
development environment of a unix system. Included are networking capabilities
thru tcp/ip aloowing one to remotely monitor/control experiments, etc etc.
There is also the advantage that it is a unix system in that many machines
in universities are unix machines running network file servers such as nfs
where one could share resources over the net and have a single type of
operating system instead of transfering from MSDOS to unix etc etc.

It also appears that NASA will be using a realtime UNIX system (i.e. LYNX OS
- a Sys V R 3.2 derivative with BSD features) for use on the space station
(for whenever it comes into being). 

The beauty of the system is that many hardware dependent functions can be 
taken over with software modules. This becomes more possible with faster and
faster micros such as the 80486, 88000, 68040 etc machines. This alows one
more flexibility in applying/changing these functions.

So in my opinion, I think many different people would have use of such
operating systems. There are many uses that probably haven't even been
considered to this point that have been hardware dependent till now.

Gerry Kokodyniak


Gerry Kokodyniak, Ph.D. Student            Department of Mechanical Engineering
kokody2@me.toronto.edu                            University of Toronto
kokody2@me.utoronto.ca                       Structural Integrity Fatigue and
kokody2@ME.UTORONTO.BITNET                     Fracture Research Laboratory
{linus,allegra,decvax,floyd}!utcsri!me!kokody2        (416) 978-6853