From:	"Alexei A. Frounze" <dummy_addressee AT hotmail DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Any comments about using RDTSC to sync code ?
Date:	Sun, 1 Apr 2001 00:49:53 -0500
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"Eduardo TUDA Lorenzetti Pellini" <dochell AT MailAndNews DOT com> wrote in message
news:3ACABB23 AT MailAndNews DOT com...
> Hi DJGPP friends,
>
> I'm doing a real time app using DJGPP that runs for almost 2 hours polling
> and
> reading some hardware ports in loops of 50 usec (*micro*seconds).
> I'm using the Pentium TSC counter to sync the data acquision since the RTC
> and
> system timer don't have this desired resolution or have some undesired
> granularity.
>
> The first problem i am living is to accurately calculate the CPU clock to
> stablish the relationship between system clocks and real time.

Just calculate average period of the clock by using RDTSC and the timer
during 1 second (you may read time from RTC instead of BIOS tick counter or
custom IRQ0 ISR). I don't know what kind of accuracy you need, but this will
probably give you satisfactory level of accuracy...

Good Luck
--
Alexei A. Frounze
alexfru [AT] chat [DOT] ru
http://alexfru.chat.ru
http://members.xoom.com/alexfru/
http://welcome.to/pmode/

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