Re: Realtime Ada Conferences

[dewar@cs.nyu.edu (Robert Dewar)]

Larry said

"<snip>
>Is anything being done to allow Ada compiler vendors to
>produce compilers that have task context switch times
>in the 20 us range?  It seems that most compiler vendors
>are not able to comply with the Ada83 tasking model
>and provide realtime context switching capabilities.

Yes, they're called faster computers. :-) Seriously, the
implication I got from what you said is that Ada compilation
systems without 20 usec context switching times do not provide
realtime context switching capabilities.  Many realtime
applications do not require this level of performance and are
nonetheless realtime.  "Realtime" implies to me predictable
timing behavior, and not some arbitrary level of performance."

Actually more and more realtime systems are being built on top of
so-called real-time systems like NT, Lynx, Chorus, or even just
Vanilla unix with Posix interfaces. I say "so-called", because
if your idea of real-time is 20 microsecond context switch (*)
then you will find that the OS already has lost the battle by
a significant factor. But, as Larry said, applications can
certainly be real-time without requiring 20 usec cst.

(*) 20 usec seems slow to me, when I was writing real-time operating
systems for Honeywell on 4MHz 8080 systems, we were aiming at better
context switching times than this :-)