Timer resolution

Joel Sherrill joel.sherrill at OARcorp.com
Fri Feb 21 13:44:32 UTC 2003

Nigel Spon wrote:
> Hi,
> If I might intrude for a moment with a simple user question; does
> anyone know where or how I might discover the timer tick interval
> limits for using the RTEMS network stack: i.e how often should
> rtems_clock_tick() be called? I ask because it must have a bearing on
> how well the TCP retransmit timers, etc will work, and I suspect there
> is a minimum resolution requirement for 10Mbit and 100Mbit Ethernet...

The tftp and ttcp demos use 10,000 microseconds as their value.  Given
that the source code is from FreeBSD, I would suspect that it doesn't 
require a clock tick lower than that.  UNIX was never known for having
low clock tick quantums.

My guess would be that anything 10 milliseconds or less would be fine.
But I would love to hear from someone else.

> Thanks for any assistance,
> Nigel
> ---
> "The Galaxy's a fun place. You'll need to have this fish in your ear."

Joel Sherrill, Ph.D.             Director of Research & Development
joel at OARcorp.com                 On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
Support Available                (256) 722-9985

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