Date:	Sun, 15 Aug 1999 14:09:13 +0300 (IDT)
From:	Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
X-Sender:	eliz AT is
To:	Simon Redwood <spredwood AT sri-net DOT demon DOT co DOT uk>
cc:	djgpp AT delorie DOT com
Subject:	Re: usleep/delay/sleep ?
In-Reply-To:	<934647567.25013.0.nnrp-11.c2de6b60@news.demon.co.uk>
Message-ID:	<Pine.SUN.3.91.990815140434.1935i-100000@is>
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Reply-To:	djgpp AT delorie DOT com
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On Sat, 14 Aug 1999, Simon Redwood wrote:

> I am new to using djgpp under dos, being a unix programmer.  I am having
> trouble with delays.
> 
> Can I rely on usleep to give me accurate timings.
> 
> Giving usleep a value of 10000-12500 produces the same delay, whereas 13000
> gives the same as 20000, where I am going wrong.

This is all expected behavior: usleep has a 55-msec granularity.  (This 
is unfortunately not stressed in the docs; v2.03 fixes that.)  The system 
clock on the PC ticks 18.2 times a second, so this is what you get.

> I would like to put a delay into a loop of about 1/100 sec. how is the best
> way to acheive this

Write your own wait loop that calls uclock.  This function has 
840-nanosecond resolution.

> I am also looking to work with microprocessors where I will need accurate
> timings of nanoseconds, how can this be best acheived.

One way is to use the machine instruction that reads the counter register 
of the Pentium and later CPUs.

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