Re: OZ-board - the text

From: Martijn van Buul (
Date: 2001-05-10 21:44:29

Bryan Pope wrote:
> > One thing is clear: forget Windows :)
> HA!  Are you sure? ;)


> > > > #### Linux ????
> > 
> I had read once about a true real-time version of Linux.  But since I don't 
> remember the web address that won't help...

That'd be RT-Linux. However, it won't be much of help. See below for 

> > > I think you can safely rule out *any* multitasking system. It introduces
> > > latencies and delays which are clearly unacceptible.
> > 
> > What about VxWorks (or any other *hard* RT system)? I would not rule that
> > out "per se". (Although, I don't think it would be highly available at the
> > hobbyist's...)
> > 
> What about QNX?  It is free*, fast and *real-time*.  You can DL the CD ISO 
> from

But it won't be fast enough.

QNX claims to be very fast (faster than VxWorks, for instance) by guaranteeing
a 6 us maximum response time unless I'm mistaken. That is a *multitude* of the
allowed deviation.

Heck, QNX claims to have a *context switch* time of only .55 us when 
running on a Pentium III. Apart from the fact that the actual context switch
is just a part of the whole aspect of response time, even the bare 
.55 us is *way* too much (And a Pentium III is a very fast machine..)

"true realtime" and "true multitasking" are mutually exclusive. You can go a
fair deal (See QNX or RT-Linux), as long as your service frequencies and
latencies are in the millisecond (or at least a reasonable fraction of a
millisecond) area, and as long as your real-time applications are mutally

RT-systems a la VxWorks, RTLinux and QNX are very interesting, and very 
powerful, but not quite up to this job.

Sorry to dissapoint you..

    Martijn van Buul - -
	 Geek code: G--  - Visit OuterSpace: 3333
   Kees J. Bot: The sum of CPU power and user brain power is a constant.
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