Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!mips!prls!philabs!sxm
From: sxm@bebop.Philips.Com (Sandeep Mehta)
Newsgroups: comp.unix.internals
Subject: Re: Can Unix sleep in terms of mili/micro?
Message-ID: <SXM.90Sep13093608@bebop.Philips.Com>
Date: 13 Sep 90 13:36:08 GMT
References: <24437@adm.BRL.MIL> <84@dlss2.UUCP>
	<MUTCHLER.90Sep11140510@zule.EBay.Sun>
Sender: news@philabs.Philips.Com
Organization: Autonomous Systems, Philips Labs, Briarcliff Manor, NY
Lines: 41
In-reply-to: mutchler@zule.EBay.Sun's message of 11 Sep 90 21:05:10 GMT
Distribution:


  james@dlss2.UUCP (James Cummings) writes:

    TAYBENGH%NUSDISCS.BITNET@cunyvm.cuny.edu writes:
      >
      >        Can Unix sleep in terms of mili or mirco second? I am aware that
      >sleep() can only sleep in terms of second. Please specify the Unix Dialect
      >when u reply. Thanks.

	      How 'bout:

      sleep_less_than_sec(x)
      int x;
      {
	      int i;

	      for (i = 0;i <= x;i++)
		      ;
      }

For many (obvious) reasons a dummy loop is not the best idea. Besides
you may not have a real time clock in your UNIX box, e.g., Sun 3's (at
least the ones I use) use the Intersil 7170 "real-time" clock in 100 Hz
periodic mode, giving a resolution of only 10 milliseconds. Using the
clock(3C) function yields CPU time used only up to a 16.667 milliseconds
accuracy.  Sun 3 (SunOS 4.0) getrusage() assumes tick intervals of
20msec, for Sun 4's 10msec. I know that struct timerval' has a "usec"
field but of course the value is hardware dependent.

You might write your own little assembler routine to use a spare counter
or something (not advisable :-)) which will suffer from all the
restrictions of the process that uses it. I know that some folks @
Berkeley have a real-time timer facility for Sun 3's under SunOS and
it's (h'ware + s'ware) pretty cheap.  But then again, is UNIX/SunOS
real-time ?

Don't know if I answered the question either ? 

sandeep
--
sxm@philabs.Philips.Com                  	"Jazz is Happiness" - Le Sony'Ra