[ntp:questions] how do I lock in average frequency correction

David Woolley david at ex.djwhome.demon.invalid
Wed Feb 15 21:13:17 UTC 2012

John Hasler wrote:
> Dave Hart writes:
>> I believe it had more to do with the Color Graphics Adapter circuitry
>> needing to operate at NTSC-compatible frequency.
> According to my Technical Reference manual the XT and the Portable PC
> used a 14.31818MHz crystal.  This was the only crystal on the
> motherboard.

Did the XT have an RTC?  The original PC certainly did not.

The AT has at least two crystals (4* NTSC and 32768kHz).

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