Experimental Physics and Industrial Control System
Subject: |
Re: EPICS periodic scan and sysClkRateSet() |
From: |
Susanna Jacobson <[email protected]> |
Cc: |
EPICS tech-talk <[email protected]> |
Date: |
Fri, 14 Nov 2003 11:44:31 -0800 |
Steven Hartman wrote:
>
> - Is there anything in base which may break or otherwise behave
> differently if the VxWorks system clock is increased to be faster than 60
> Hz? Looking at dbScan.c, it looks like the periodic scan rate will do the
> right thing (so long as sysClkRateSet() is called before initPeriodic(),
> so before iocInit()). drvTS.c also looks OK. Anything else in base that
> may be a problem? (I will of course check device code, sub records, etc
> which are used in the app which are not in base.)
The ALS control system includes 15 MCP750 (compact PCI Power PC, 3 235MHz
and 12 367MHz) IOCs with a system clock rate of 100Hz that have been running
with no problems for > 2 yrs.
> - Does anyone have experience on a maximum reasonable VxWorks clock rate
> with an EPICS application? Same caveats as above, but a rough guideline
> would be useful.
We tried running the 12 367MHz CPUs with a clock rate of 1000Hz, but then
we saw network operations running out of memory buffers, causing channel
access connections to be dropped. No testing at intermediate clock rates
was done. So my guess is that the maximum reasonable rate is somewhere
between 100Hz and 1000Hz.
Susanna
--
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Susanna Jacobson MS 10-110
[email protected] Lawrence Berkeley National Laboratory
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