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From: tmoran@bix.com (Tom Moran)
Subject: Re: System Clock update rate of 0.055 milliseconds in DOS/Win95 and
 Ada.Calendar
Date: 1999/01/10
Message-ID: <36993048.831644@news.pacbell.net>#1/1
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References: <01be3c40$f93dc120$3804fbd1@longslide>
 <36984ebc.31381254@news.pacbell.net> <01be3cc8$0d0af420$3304fbd1@longslide>
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Newsgroups: comp.lang.ada
Date: 1999-01-10T00:00:00+00:00
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I happen to know the Janus Ada.Calendar.Clock uses the Windows API
call QueryPerformanceCounter to get the time since boot in clock ticks
(0.055/2**16=0.9 mics).  If you aren't using the Janus compiler, you
could still build your own clock routines that way to give you a clock
that changes value more often than every 55 ms.  If you need to do
something like update the screen, or start a sound periodically, but
more accurately than 55ms resolution, you can do the equivalent of,
say, "delay 0.001;" by polling that hires clock.
  If you really need interrupts - ie, polling won't do what you need,
and you need them more often than every 55ms, then there are some
tricks you could do like sending dummy data out a serial port and
using those interrupts for timing, but I'd be surprised if Win95
allowed you to actually reprogram the clock tick time.  If it does
allow it, I suggest "Programmer's Problem Solver for the IBM PC, XT, &
AT", ISBN 0-89303-787-7, which has good info on various such low level
fiddling.