RE: [Off-Topic]" Real-Time" extensions to NT

Gregory_G._Dyess

Let me start by saying I am an NT/W2K bigot and recommend it for many
things. I would not use NT, with or without extensions, for "hard
real-time". Its interrupt latencies are far too long and unpredictable for
this use and I don't trust any of the real-time extensions. Period.

Depending upon the requirements, you may consider a client/server style of
architecture. You could use something more suited to real-time (QNX, Wind
River Tornado, iRMX/InTime, Windows CE or even roll-your-own if it's
small/simple enough) as your real-time engine and use NT as you HMI. This
has been done successfully by several DCS (Distributed Control System)
vendors for a few years now.

Just my $0.02 (US) worth.
Greg

> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of
> [email protected]
> Sent: Tuesday, June 13, 2000 7:57 AM
> To: NT Developers Interest List
> Subject: [ntdev] [Off-Topic]" Real-Time" extensions to NT
>
>
> Hi all,
>
> This topic comes up every now and then -- sorry if this has been answered
> before.
>
> Has anybody had any experience (good or bad) with real-time
> "extensions" to
> NT? A while back, our company had investigated products such as
> HyperKernel, but ended up not using them because the scope of the
> projects
> we were involved with did not truly require "real-time" performance. We
> currently stuff National Instruments' data acquisition & control
> cards in a
> PC, and write custom software to interface to them. Not exactly
> "real-time" in any sense of the word, but adequate up to now beacuse the
> control requirements were not stringent.
>
> Now the question of "real-time" has come up again here (more
> stringent PID
> control requirements), and although I'm a firm believer that
> "real-time" is
> not possible under NT (or W2K, or any other general-purpose OS), I'm
> charged with re-investigating the possibility of using such
> extensions (or
> finding other solutions) "Other people do real-time control in
> Windows" I
> hear from higher ups here -- but I'm not buying it -- not yet anyway.
>
> All the information I've read suggests that interrupt latency is not
> predictable, and built-in timer performance is not predictable.
> So without
> a predictable stable time-base, stable control (in my opinion) cannot be
> assured. I must admit that I'm biased toward using devices that
> have their
> own microcontrollers (and dedicated software/firmware) on them, but
> nonetheless, I'd like to hear from anyone who's had any
> experience with the
> NT "extensions" or similar solutions.
>
> Thanks in advance for any thoughts or suggestions.
>
> -bill
>
> ---------------------
> Bill Christie
> Link Engineering Company
> www.linkeng.com
>
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