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Date:	Sun, 30 Apr 2000 12:59:03 PST
From:	Peter Skye <pskye@peterskye.com >
Reply-To:	scoug-programming@scoug.com
To:	scoug-programming@scoug.com
Subject:	SCOUG-Programming: OS/2 as real-time OS ?

Content Type: text/plain

Steven Levine wrote:
>
> One thing to keep in mind, is real-time is a
> performance requirement, not an OS component.

Correct. You specify what latency you can live with, and design from
there.

The fastest response comes from dedicated hardware, and I don't mean
"computer" hardware. I'm talking analog -- opamps with fast slew rates
or whatever. It's been a few years since I designed analog pc boards
(remember Bishop Graphics and all their circuit design stickies?), but
even back then the response was "instantaneous". I _think_ slew rates
are about 20 volts/usec these days for an off-the-shelf opamp.

> I would consider OS/2 good for what I call soft real-time
> jobs where response times in the 1 mSec range are sufficient.

That's the kind of thing I'm interested in. _Why_ is "1 msec" the point
where you feel OS/2 "hits the wall"?

> Hard real-time, for me, is when you start
> looking a sub 100 uSec response times.

Is the amount of latency in the OS/2 interrupt handler enough to keep
OS/2 from achieving a 100 usec response time?

> Also, you can always achieve reduced response
> time by doing more work in the interrupt handlers,
> or in the case of OS/2, using context hooks.

Hah, you got me. What is a "context hook"?

- Peter

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