[Coco] CoCo's TIMER and 60hz

Gene Heskett gheskett at shentel.net
Thu May 30 15:17:01 EDT 2019

On Thursday 30 May 2019 02:33:17 pm Brock Harrison wrote:

> Of course, the interminable VSYNC cycle length renders my initial
> suggestion impractical.  My apologies.
> Still, evaluating age-related frequency drift seems worthwhile to
> consider.  Two options present themselves:
> 1) Alternatively measure E or Q clock signal frequency, which may not
> require such precision, with the assumption that VSYNC always remains
> a uniform fraction of primary clock speed (Is this strictly true?)

Yes unless some of John K.'s double speed hacks have been done to the 
motherboard. My guess is that you could count the world wide number of 
those conversions on one hand.

> 2) 
> Develop a small cartridge based device that measures those signals,
> with a small wire to attach to specific motherboard signal lines. 

If measuring E clock, thats all on the cartridge port.

> (Precisely recording such signals requires what micro-controller clock
> frequency?) Create a limited set of such devices and trade among the
> community over time to create the dataset.

Maintaining the accuracy of such a gizmo to generate real data as its 
shipped around would be iffy, probaby best if it contained an SDR chip 
so it could be twiddled to match wwv at 10 mhz.  Then all the user would 
need is a nylon rweeker and 20 feet of antenna wire, the higher the 

> BH

Cheers, Gene Heskett
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