Real-Time Granularity: A Query

[Bret Orsburn]

Here is a question for the Unix Wizards (Any of you left out there? :-)

How coarse is the real-time base on *real* Unix machines?

The gettimeofday function returns (in part) a microsecond resolution counter.
The docs I have found so far indicate that this counter is really just bumped
by the system tick interrupt at a 50-100 HZ rate. Is that a useful
generalization? Are there any significant counter-examples?

Some context:

I am contributing to the design of a stand-alone system that will run some
code ported from a Unix environment. This code uses the gettimeofday system
call to derive a millisecond-resolution timestamp.

If *real* Unix just bumps this counter 50-100 times per second, I can
immediately recommend that behavior as a minimum system capability. I can
then take steps to determine if there is any real benefit in exceeding this
minimum capability.

TIA, Wizards.
-- 
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bret at codonics.com
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Bret Orsburn