[time-nuts] PC clock generator without 14.318MHz

Magnus Danielson magnus at rubidium.dyndns.org
Tue Oct 18 17:36:55 EDT 2016


Poul-Henning,

On 10/18/2016 10:38 PM, Poul-Henning Kamp wrote:
> --------
> In message <ep0d0ctbrovmisvj43j57ns6smt606t3fs at 4ax.com>, Gary Woods writes:
>> On Tue, 18 Oct 2016 16:53:15 +0200, you wrote:
>>
>>> 14.317 MHz quartz.  Such frequency is a relic of original PC design
>>
>> It's 4X the color subcarrier frequency in NTSC (originally U.S.)
>> television; rapidly becoming a dinosaur. I'm sure it was used in computers
>> to make color video easier. Newer boards doubtless use much faster clocks
>> and synthesize what the parts need.
>
> It's 14.3181818 MHz and it has a most facinating history - if you care
> for that sort of thing:
>
> 	https://en.wikipedia.org/wiki/Colorburst#Rationale_for_NTSC_Color_burst_frequency

To this day, the 1.001 factor haunts us in all modern hardware and 
timing designs, including the latest synchronization standards.

It's fascinating that we have been simulating several centuries into the 
future to ensure that the algorithms for the synchronization will make 
the 1.001 factor keep working as intended. I wrote one such simulator 
being used.

Cheers,
Magnus


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