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From: rainer@boulder.Colorado.EDU (Rainer Malzbender)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Accurate timing request
Message-ID: <1991Mar14.091249.11341@colorado.edu>
Date: 14 Mar 91 09:12:49 GMT
References: <1991Mar6.145414.8747@uwovax.uwo.ca> <1991Mar7.025205.9213@qualcomm.com> <1991Mar14.040625.13212@comp.vuw.ac.nz>
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In article <1991Mar14.040625.13212@comp.vuw.ac.nz> Timothy.Litton@comp.vuw.ac.nz (Tim Litton) writes:
>
>In article <1991Mar7.025205.9213@qualcomm.com>,
>rdippold@maui.qualcomm.com (Ron Dippold) writes:
>|> In article <1991Mar6.145414.8747@uwovax.uwo.ca>
>|> bangarth@uwovax.uwo.ca writes:
>|> >Researchers here are looking for some facility to measure time with
>|> 1 ms. 
...
>
>Don't try this!!!
>
>Your system clock is dependent on that timer, so are most of your I/O
>devices for time outs!  Personally, I would put up the +/- 5ms
>inaccuracy then try this!

Nonsense. You intercept the interrupt vector with your own routine, then
call the regular interrupt once every N times. Everything works, except
you eat up more CPU time handling all the extra interrupts. Basic does
exactly this - it reprograms the timer to interrupt four times faster
in order to produce more accurate timing for sound.
--
Rainer Malzbender PhD   "It's not the bullet that kills you, it's the hole."
Dept. of Physics (303)492-6829                             -Laurie Anderson
U. of Colorado, Boulder         rainer@boulder.colorado.edu 128.138.240.246