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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: Realtime Extensions for Windows NT
Date: 1997/05/25
Message-ID: <dewar.864557434@merv>#1/1
X-Deja-AN: 243784540
References: <3385CAC3.3EEE@eideticscorp.com>
Organization: New York University
Newsgroups: comp.lang.ada
Date: 1997-05-25T00:00:00+00:00
List-Id: <comp.lang.ada>


Matthew says

<<I am looking into realtime operating systems for an aircraft simulator
I am working on.  I am trying to decide whether to use realtime
extensions for Windows NT such as Radisys' InTime or Imagination's
Hyperkernel or proprietary realtime operating systems such as LynxOS or
QNX.  I would appreciate feedback from anybody who is currently using
InTime or Hyperkernel and would know about the determinancy of each
operating system's behavior.>>

I assume you are interested in Ada on these systems (or why would you be
posting here?) Given this, one thing to realize about determinacy is that
the Ada tasking model is entirely deterministic if Annex D is fully and
completely supported. Check validation VSR's carefully to ensure that all
tests that are relevant in annex D are passed. There are a few annex D
tests which are legitimately optional (notably the ones for Asynchronous
Task Control), but these are the only ones that should be missing. If the
implementation passes 100% of these tests, you have a pretty good indication
that the underlying task control system is acceptably deterministic.

This is a fairly strenuous requirement. In our experience, many operating
systems level thread support packages do NOT meet these requirements. For
example, with the Solaris implementation of GNAT, we find that the Solaris
system threads do not quite meet the requirements, even if you run in realtime
mode in super user state. To pass all the annex D tests, we had to use our
own threads package. A future version of the Solaris GNAT will come packaged
with a choice between the two threads support options.

Another possibility for you to consider is Linux operating with the
FSU threads package, which passes 100% of the annex D tests.