Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!ucsd!nosc!manta!north
From: north@manta.NOSC.MIL (Mark H. North)
Newsgroups: comp.lang.pascal
Subject: Re: Timing in Turbo Pascal
Message-ID: <1308@manta.NOSC.MIL>
Date: 31 Oct 90 03:10:05 GMT
References: <2280@oucsace.cs.OHIOU.EDU> <5307@crash.cts.com>
Reply-To: north@manta.nosc.mil.UUCP (Mark H. North)
Distribution: na
Organization: Naval Ocean Systems Center, San Diego
Lines: 24

In article <5307@crash.cts.com> nkraft@crash.cts.com (Norman Kraft) writes:
>
>Before you start this project, look at Abrash's "Zen of Assembly Language".
>In the first several chapters he developes an assembler routine which does
>not depend on the BIOS, but uses timer chips in a very efficient and 
>accurate way. The "ZenTimer", as it is called, achieves a resolution
>of 1 microsecond (1 millionth of a second), and uses the 8253. Abrash
>uses it to time 4 cycle assembler routines: a serious challenge, that!
>
I find this hard to believe (microsecond accuracy). There are hardware
interrupts going on at unpredictable times so unless you take over the
whole machine (memory refresh and all...) how can you be assured of accuracy
in your timer function?

Mark



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