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From: lauren@vortex.UUCP (Lauren Weinstein)
Newsgroups: net.micro.pc
Subject: more on use of interval timer in PC vs. timing loops
Message-ID: <462@vortex.UUCP>
Date: Thu, 6-Dec-84 01:03:58 EST
Article-I.D.: vortex.462
Posted: Thu Dec  6 01:03:58 1984
Date-Received: Sat, 8-Dec-84 04:51:24 EST
Organization: Vortex Technology, Los Angeles
Lines: 16

After some checking, it turns out that there are even more
reasons NOT to directly use the interval timer:

1) Of the three ports on the unit, one handles dynamic refresh.
2) Another port is connected directly to the audio speaker.
3) The last provides "real time clock ticks" at a fixed
   rate of approx. 18.2/sec on the "real" PC/XT/AT.  There is no
   guarantee of the same rate on PC clones of various sorts.

Given that none of these ports can be "diddled" without damaging
other important functionality, and given that a fixed interrupt
rate of approx. 18.2 isn't terribly handy (or even USABLE) in
many applications, this still leaves only timing loops in a
large number of situations...

--Lauren--