RES: Different tick interval with the same application between RTEMS 4.10.0 and 4.10.2?

Fabrício de Novaes Kucinskis fabricio at
Mon May 21 17:55:34 UTC 2012

Hi Joel, and thanks for your answer,


The “one second” reference I used is real time (ERC32 BSP). When simulating
(SIS BSP), things run a little faster. But not as fast as what we are seeing


We checked (both a dump of the .exe and with a breakpoint at Clock_isr), and
the fast idle mode is not #included in the application compiled for SIS. 


Could this be a side-effect of the nanoseconds change? I don’t think so, as
we’re not enabling the extension. But don’t know where else to look for.


We also compiled the same application with both versions of RTEMS and run in
an ERC32 board. Both run at the same 1-second interval. As this is our main
target, the issue with the simulator shouldn’t bother us too much. But I
think it’s always important to report to the list when something doesn’t
work as expected – maybe the observed behavior point to something to be
improved or fixed.


Thanks again,






De: Joel Sherrill [mailto:joel.sherrill at] 
Enviada em: segunda-feira, 21 de maio de 2012 11:26
Para: Fabrício de Novaes Kucinskis
Cc: 'RTEMS Users'
Assunto: Re: Different tick interval with the same application between RTEMS
4.10.0 and 4.10.2?


On 05/21/2012 08:49 AM, Fabrício de Novaes Kucinskis wrote: 

Hi all,


We've just upgraded our development environment from RTEMS 4.10.0 to RTEMS
4.10.2. As always, an interesting issue has raised! ;-)


We use the ERC32 and SIS BSPs. After the upgrade, a simple test application
that prints a clock once per second started to print the clock values almost
two times faster on SIS. The application gets the number of ticks per second
and uses it in the rtems_task_wake_after directive.

When on any simulator, there is always the possibility that somehow the fast
idle mode
in the clock driver got turned on.


To determine if the issue was on SIS or RTEMS, we run in the 4.10.2
environment the previous version of the test, compiled with RTEMS 4.10.0,
and the task runs once per second. Also, the number of ticks per second
reported in both versions is the same.

Is this once per second in simulated or real time?

Set a break point at Clock_isr and see if it is doing the fast idle mode.


Looking at the release notes, we've found a number of changes/fixes related
with ticks and time since 4.10.0. But it seems that none of them is related
to what I report here.


I looked at the diff files and the only changes are fixing bugs 
related to nanoseconds since last tick when you ask on the
edge of a tick interrupt occurring.

Is this something to be expected when upgrading? Am I missing some change in
the configuration?


Thanks in advance and best regards,


Fabrício de Novaes Kucinskis.

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