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From: thyssen@batserver.cs.uq.oz.au (Anthony Thyssen)
Newsgroups: comp.sys.amiga.tech
Subject: Micro Timing Critical sections HELP!
Message-ID: <4934@uqcspe.cs.uq.oz.au>
Date: 20 Sep 90 02:06:45 GMT
Sender: news@uqcspe.cs.uq.oz.au
Reply-To: thyssen@batserver.cs.uq.oz.au
Lines: 37



   Hello AmigaLand,
		   I am desperately tring to do some timing of a
section of C code and any help would be appreciated.

   Currently I am using both CIA-B timers (linked) to count pulses on
the `PHI2' or in 68000 parlance `E' line. This gives a timer able to
measure periods of up to about 1 hour! duration.

   I calculated that the `E' line should be runing at .715Mhz (1/10th
of cpu clock rate) and physical measurments (a stop watch over ~20mins)
give a figure of .709 +/- .001 Mhz (3 measurements were made).

   Timing a fixed loop of code (see below) however produced varing
results which I beleave is due to the interupt handling of the CPU.

IE with the full screen visible this timed to about 42440 +/- 10 `E' ticks.
Moveing the screen then so only the title bar was showing (while timing)
produced a much lower value (varing a good deal) of 40200 +/- 60 `E' ticks.

I am using Disable() during the timed period to stop other tasks. 

QUESTIONS :-
 1)  What is the differance bettween Disable-Enable
   and Forbid-Permit exec library calls?
 2)  How do you blank the screen?
 3)  Is there any other interupts which can be disabled? How?
 4)  Under the above can memory still be allocated/deallocated - Important?
 5)  Any other comments.

  Anthony Thyssen - (Dragon Computing!)         thyssen@batserver.cs.uq.oz.au
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      In some parts of the city curiosity didn't just kill the cat,
    It threw it in the river with lead weights tied to its feet.
						-- Terry Pratchett "Sourcery"
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