On Tue, 15 Mar 2011, Joel Jacobs wrote:

> Date: Tue, 15 Mar 2011 15:22:04 -0400
> From: Joel Jacobs <[email protected]>
> Reply-To: "Enhanced Machine Controller (EMC)"
>     <[email protected]>
> To: [email protected]
> Subject: [Emc-users] unexpected realtime delay
> 
> Hi,
> Is there any way to adjust the sensitivity or suppress this  error?  I
> have an Atom D525 running the latest EMC2 from the repositories
> (Ubuntu 10.04).  I have a Mesa 7I43 and Gecko 320 servo drives.  I
> have no base thread at all, just the servo thread running at 700us. At
> 1ms I would get random 'thunks' from the servo only while jogging the
> X axis in the + direction at 120ipm. Minus X Jogs were smooth.
> After adjusting the servo thread to 700us all motors are super smooth
> no matter what.  Just randomly getting this error - sometimes takes an
> hour to pop up.  Like I said, the motors are running great so I don't
> really want to tweak the hyperthreading and isocpu= stuff.  I don't
> understand why I'm getting this error with no base thread.  Thanks,
> Joel Jacobs



You will still get "unexpected realtime delay" errors with just a servo thread 
if the latency gets to be more than 120% of the servo period (this would be 
200 uSec at a 1ms servo thread period) This is a fairly serious amount of 
latency and probably should be looked into. I suspect your random 
"thunks" are also latency related. Possible fixes:

Disable SMI

Disable screensaver

Make sure all power management is off in BIOS

Disable monitor mode-set

setting a reasonable value of stepgen maxaccel in the HAL/INI file will make 
the hardware stepgen more tolerant of latency

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Peter Wallace
Mesa Electronics

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