[ntp:questions] Time server question

Gabs Ricalde gsricalde at gmail.com
Fri Jul 19 18:26:08 UTC 2019


On Wed, Jul 17, 2019 at 7:59 PM William Unruh <unruh at invalid.ca> wrote:
> I suspect it will be a bad outcome. The rpoblem is that you get
> interrupt contention, and the two interrups will put in time delays into
> the second one processed.
>

That was my observation when I did some tests years ago with a single core Atom.

With a dual core CPU, the interrupts can be simultaneously handled by
both cores. In the attached plot, the parallel port timestamps are
ahead by around 3 us, probably due to the RS232 line driver/receiver.

When only one core is enabled, the serial port is handled first
followed by the parallel port which causes a delay of around 10 us.
The delay disappears when the serial port source is disconnected.


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