[time-nuts] GPS clock to RT-Linux for pulsar machine

Magnus Danielson cfmd at bredband.net
Sat Jul 2 13:00:30 EDT 2005

From: "John Miles" <jmiles at pop.net>
Subject: RE: [time-nuts] GPS clock to RT-Linux for pulsar machine 
Date: Sat, 2 Jul 2005 09:26:04 -0700

> You can always crank up the clock rate in a custom application and generate
> the 18.2 Hz system timer interrupt yourself, though.  There's nothing
> inherent about DOS that prevents you from doing precision timekeeping with
> it.
> That's not to say it's fun.

Indeed. It is clocked at 14,31818 MHz / 12 = 1,1921816666... MHz and 18.2 MHz
comes from the divition with the maximum factor of 65535. Since you can read
the states from all three oscillators you can do alot. Using two of them and
setting relative prime division factors create the basis for a 32 bit counter
with about 838 ns step resolution. An otherwise idle processor can do counter
and parallel polling/writing if you like. You should be able to acheive the
same result on RTLINUX or even LINUX if you treat it propperly, but you have to
fiddle more with the OS than DOS forces you to do.


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