Re: Real time?

[shackle <shackle-at-cme.nist.gov>]

My 2 cents worth on QNX.

There is another factor that might prevent porting of EMC to  QNX, or another
RTOS for embedded applications. That parameter is the schuduling resolution. 
Under Linux, another unix-like commercial real-time operating system, a couple
of years ago the best scheduling resolution we could get was 5 milliseconds.
Under VxWorks, a not very unix-like commercial RTOS, the best I could get was
500 microseconds.  I haven't seen anything that compares with the 15
microseconds that RTlinux can deliver.

The main reason is that RTLinux allows a lot less flexibility and provides
fewer functions to real-time application programmers  than those commercial
systems. In those RTOS's "real-time" programs can read/write files,
send/recieve data over a network and  dynamically allocate/deallocate  memory.
(Although programmers need to be extremely careful when doing these things or
the program will no longer be deterministic.) In RTLinux, you can't do any of
these at all. This might be a good thing, just to prevent errors. But it has
also allowed RTLinux to get much better scheduling resolution.

Does anybody happen to know what kind of scheduling resolution is possible
under QNX? I couldn't find the info on their web page.

-- Will