[Coco] CoCo's TIMER and 60hz

Gene Heskett gheskett at shentel.net
Thu May 30 14:52:39 EDT 2019

On Thursday 30 May 2019 02:12:15 pm Dave Philipsen wrote:

> I think all *real* CoCos would nominally have the same VSYNC
> frequency. As far as finding a ‘test point’ on the system board to
> read the frequency, that would be fine but to be able to tune down to
> an accuracy of around +/- one second per day (which I think a good
> mechanical automatic wristwatches could achieve) you’d have to have a
> pretty accurate frequency counter that could differentiate between,
> say, 60 Hz and 60.0007 Hz.
> Dave

Many modern scopes determine the frequency by measuring the period 
between the trigger points, and calculating the recprocal. with a 10 to 
100 mhz reference, they can be very accurate at the lower freqs. 
> > On May 30, 2019, at 12:51 PM, Brock Harrison
> > <brock.erific at gmail.com> wrote:
> >
> > Might there perhaps exist a document illustrating the various
> > models' VSYNC frequencies, if they differ, and that which can also
> > provide some easily accessible locations on various motherboards so
> > as to validate current machine operation against these values?
> >
> > If so, the action of compiling a large list of empirical values from
> > users and plotting the deviation from nominal may suggest emulation
> > improvements and define soft real time clock module complexity
> > requirements.
> >
> > BH
> >
> > --
> > Coco mailing list
> > Coco at maltedmedia.com
> > https://pairlist5.pair.net/mailman/listinfo/coco

Cheers, Gene Heskett
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