[time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

Magnus Danielson magnus at rubidium.dyndns.org
Sun Dec 2 00:53:07 UTC 2012

On 12/02/2012 01:29 AM, David wrote:
> Originally the IBM PC design used an 8253 or 8254 PIT, programmable
> interval timer, located at ports 40h to 43h with Timer 0 clocked at
> 1.193182 MHz (1/3rd of 3.579545 MHz or 1/12th of 14.318 MHz) and set
> to divide by 65536 which generated about an 18.2 Hz interrupt rate on
> IRQ 0.  Timer 1 generated the since deprecated DRAM refresh clock and
> Timer 2 goes to the PC speaker.

In a modern world, look for things like HPET and TSC:


You want to get a better reference clock to these timers.


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