The rate you do the things you do...

The rate you do the things you do...

[David Weller]

I have a feeling this will raise more questions than answers, but here
 goes...


I'm trying to cut through the hype and understand whether Windows NT
can support "simulation software" rates in the 30-60Hz range.  We have
a, um, enthusiastic MS supporter that sez, "Sure, no problem!".
Before I expend labor hours attempting to prove them wrong (or right,
for that matter), I'd be interested in feedback from anybody else in
this community that has gone through such a venture yet.  We're not
looking for hairy details, just a general range for now (tops out at
10Hz? 5Hz?).  I personally am VERY leery of a "business-based" OS
being able to support real-time scheduling rates, but we have a lot of
management pressure to examine PC-based COTS products for future
approaches.  This ain't my idea, folks, but I do have a professional
responsibility to shoot it down^H^H^H^H^H^H^H^H^H^H^H^H^H examine its
potential :-)

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Re: The rate you do the things you do...

[steved]

David Weller writes:
>I have a feeling this will raise more questions than answers, but here
> goes...
>
>
>I'm trying to cut through the hype and understand whether Windows NT
>can support "simulation software" rates in the 30-60Hz range.  We have
>a, um, enthusiastic MS supporter that sez, "Sure, no problem!".
>Before I expend labor hours attempting to prove them wrong (or right,
>for that matter), I'd be interested in feedback from anybody else in
>this community that has gone through such a venture yet.  We're not
>looking for hairy details, just a general range for now (tops out at
>10Hz? 5Hz?).  I personally am VERY leery of a "business-based" OS
>being able to support real-time scheduling rates, but we have a lot of
>management pressure to examine PC-based COTS products for future
>approaches.  This ain't my idea, folks, but I do have a professional
>responsibility to shoot it down^H^H^H^H^H^H^H^H^H^H^H^H^H examine its
>potential :-)
>
I am looking forward to hearing other responses.  We are using NT for what
we call our "GUI Router".  An embedded computer sends data to the GUI Router
which relays the message to a Workstation using TCP/IP sockets.  I have
seen good results... except when doing disk accesses on the system running
the GUI Router with other applications, at which time there are significant
delays.

We are running our GUI Router at "high" priority, and will soon try running it
"real time" to see if we can get rid of delays during disk access.

With our current arrangement 1K makes it round trip in approx 30 msec.

Steve Doiel

Re: The rate you do the things you do...

[Tarjei T. Jensen]

> Steve Doiel wrote:
>
> We are running our GUI Router at "high" priority, and will soon try running it
> "real time" to see if we can get rid of delays during disk access.
> 

Have you tried to use OS/2 Warp (or the upcoming Merlin version) with real time 
priority for the server?

Greetings,

Re: The rate you do the things you do...

[Theodore E. Dennison]

David Weller wrote:
> 
> I have a feeling this will raise more questions than answers, but here
>  goes...
> 
> I'm trying to cut through the hype and understand whether Windows NT
> can support "simulation software" rates in the 30-60Hz range.  We have
> a, um, enthusiastic MS supporter that sez, "Sure, no problem!".
> Before I expend labor hours attempting to prove them wrong (or right,
> for that matter), I'd be interested in feedback from anybody else in
> this community that has gone through such a venture yet.  We're not
> looking for hairy details, just a general range for now (tops out at
> 10Hz? 5Hz?).  I personally am VERY leery of a "business-based" OS
> being able to support real-time scheduling rates, but we have a lot of
> management pressure to examine PC-based COTS products for future
> approaches.  This ain't my idea, folks, but I do have a professional
> responsibility to shoot it down^H^H^H^H^H^H^H^H^H^H^H^H^H examine its
> potential :-)


I've been using NT for about a year now for a "real-time" project with a
1HZ update rate (any sneers you have at 1HZ real-time, I share with you).

One thing I have found, though, is that NT supports an equivalent to a
real-time clock. It is called the "Multimedia timer". Its highest 
effective resolution is about 55 milliseconds (good for up to 18 Hz, if
my math is good). It calls a user-specified routine at interrupt 
priority (higher than any process. All of NT's other timing mechanisms
are message-based, which is unacceptable for a hard real-time application.

If you need better than 18 Hz (and it looks like you do) you would have
to find a third-party real-time clock with NT drivers. Good luck!
(tell me if you find one).

Don't be so quick to dismiss NT though. The more I work with it, the
more impressed I am. Internally, it is very Unix-like. I'd wager that
your average VMS or Unix (non-GUI) application could be ported to 
WindowsNT with minimal effort.

-- 
T.E.D.          
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