I use this version of the kernel and have for a while, latencies seems good 
then running for a short while. I know I tested earlier and think something 
happened with like a few minutes in between.

I am working in the direction to run real time on something else than ordinary 
computer for several reasons. These small raspberry or beagle bones might be a 
good option for several reasons: Price, power consumption, to some degree 
needed space and a few more.

The tasks are few: emctask, emcmot, emcio and upstream communication. I have 
started to look in the code and think the GUI is the most complex part. As is 
now there is NML communication in between but machinekit i heard have replaced 
with 0MQ. I have only been able to run NML locally.


> So if I am reading your message correctly, preempt’s latencies are not 
> typically as good as RTAI?  Will there be an RTAI kernel for Stretch at some 
> point?   
> Thanks,
> -Tom
> 
> > On Jul 21, 2017, at 8:25 AM, Jeff Epler <[email protected]> wrote:
> > 
> > I've been working on a live+install image of Debian Stretch with
> > * The just-released LinuxCNC 2.7.10
> > * kernel 4.9.0-3-rt-amd64 or 4.9.0-3-rt-686-pae
> > * xfce desktop (same desktop we used on wheezy)
> > * goodies like hostmot2 firmwares, truetype-tracer, f-engrave
> > 
> > This image is based on the "PREEMPT RT" kernel, which typically
> > gives latencies good enough for FPGA-based systems, though often the
> > latency is too high for software encoder and stepgen systems.
> > Assuming you have a multi-core system, isolating the highest
> > numbered CPU with isolcpus=# on the kernel commandline may help
> > latency, just as with RTAI.
> > 
> > Unless you know your computer only supports 32-bit code, I recommend
> > using the -amd64 image, which works for both AMD and Intel 64-bit
> > CPUs.
> > 
> > Like the older images, you can either boot live to test your
> > hardware, or install to the hard disk, from the same iso image.
> > 
> > The Debian image is a "hybrid" iso, which means you can use the same
> > iso file for a USB stick or a DVD.  (The image is bigger than a
> > traditional CD, so you can't install from regular CD anymore.)
> > Instructions for writing the image to a USB stick from Windows and
> > Linux are here: 
> > 
> > http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Hybrid_Iso
> > 
> > **NOTE** the Ubuntu "startup disk creator" and unetbootin do NOT
> > handle hybrid images.  Use the above instructions instead, if you
> > want to install from USB.  To install from DVD you can use any
> > traditional method to write the iso image.
> > 
> > You can find it at the temporary URL
> > http://www.linuxcnc.org/testing-stretch-rtpreempt/
> > 
> > For more notes and for the scripts used to build these images,
> > see https://github.com/jepler/stretch-live-build
> > 
> > The github repository has an "issues" section.  Please use it only
> > to file bugs about the image itself, not about bugs in LinuxCNC,
> > even if the bug in LinuxCNC seems to be specific to Debian Stretch.
> > (but if you aren't sure, then file it in stretch-live-build and
> > we'll triage it)
> > 
> > Jeff
> > 
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> 
> 
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