7i80 and 7i77

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18 Sep 2015 20:48 #62749 by PCW
Replied by PCW on topic 7i80 and 7i77
what does uname -a print?

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18 Sep 2015 21:43 #62754 by jeeybee
Replied by jeeybee on topic 7i80 and 7i77

what does uname -a print?


Linux cnc 3.2.0-4-rt-686-pae #1 SMP PREEMPT RT Debian 3.2.68-1+deb7u3 i686 GNU/Linux

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18 Sep 2015 21:49 #62755 by andypugh
Replied by andypugh on topic 7i80 and 7i77
I think what your data-points show is that the system has decent RTAI latency, but not good RT_PREEMPT latency.

It is possible that you have a legacy-USB problem and an SMI problem, and it is probably worth trying to fix both before finally giving up.

Bear in mind that a motherboard is one of the cheapest parts of the CNC system, and rejected ones may find uses elsewhere.

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18 Sep 2015 22:14 #62757 by jeeybee
Replied by jeeybee on topic 7i80 and 7i77
Yes, but also when I now boot with the RTAI kernel its the same bad latency as if I boot with RT_PREEMPT so the installation of RT_PREEMPT seem to have made the other worse too.
So it would be interesting to know what the installation of RT did to make the RTAI be just as bad.

Its not only the price but more the size and how smooth this little box fit right back on a lcd screen.

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18 Sep 2015 23:22 #62759 by PCW
Replied by PCW on topic 7i80 and 7i77
I doubt that installing the Preemt-RT kernel can affect anything when running the RTAI kernel
its more likely something else global that you changed (grub settings BIOS settings etc)

At this point to make sure, I would boot from the live wheezy image,
and run the latency test for a few hours while running glxgears, videos etc.

If you cannot get the latency < 75 or so uSec with the wheezy RTAI image
it really looks like that motherboard is not usable for linuxcnc

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19 Sep 2015 02:33 - 19 Sep 2015 02:35 #62766 by jeeybee
Replied by jeeybee on topic 7i80 and 7i77
Nope, yesterday I reinstalled everything (formated the drive) and I only did these steps after updating to linuxcnc 2.7 and tried the latency after every step.

sudo apt-get update
sudo apt-get dist-upgrade
sudo apt-get install linux-image-rt-686-pae.

Here it was still ok

sudo apt-key adv --keyserver hkp://keys.gnupg.net --recv-key 8f374fef
Added new source deb linuxcnc.org/ jessie base 2.7-uspace
sudo apt-get update
sudo apt-get install linuxcnc-uspace.

After this it was as bad as I stated before and it doesnt matter which kernel I boot.
Last edit: 19 Sep 2015 02:35 by jeeybee.

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19 Sep 2015 02:42 #62767 by PCW
Replied by PCW on topic 7i80 and 7i77
Strange, maybe you lost some grub settings with the new kernel
?

When you say the stock install was OK, what was the latency after an hour or so of videos?

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19 Sep 2015 18:52 #62780 by jeeybee
Replied by jeeybee on topic 7i80 and 7i77

Strange, maybe you lost some grub settings with the new kernel
?

When you say the stock install was OK, what was the latency after an hour or so of videos?


Reinstalled the stock install again to try it from there and after a Grub tweak (isolcpus=1 acpi_irq_nobalance noirqbalance)
I got a maximum of 24000ns after youtubing an hour, mostly about 10000ns, before that I got 200000ns spikes.
I also tried this with the RT PREEMT with no succes.

So it seem the computer is fit for LinuxCNC with the stock install and this is even with default settings in BIOS.

What could it be that messes it up??

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19 Sep 2015 20:43 #62781 by jeeybee
Replied by jeeybee on topic 7i80 and 7i77
Are there any other kernels or some other workaround I could try?

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19 Sep 2015 22:12 - 20 Sep 2015 20:05 #62783 by PCW
Replied by PCW on topic 7i80 and 7i77
another PC? :-)

You could try an up-to-date Preempt-RT kernel (4.1.5 is the latest I think)

Here's a script that works on Ubuntu 14.04, might work on Wheezy

cd ~
sudo apt-get update
sudo apt-get install build-essential bin86 kernel-package libqt4-dev libncurses5
-dev pkg-config
mkdir rtlinux
cd rtlinux
wget ftp://ftp.kernel.org/pub/linux/kernel/v4.x/linux-4.1.5.tar.xz
wget www.kernel.org/pub/linux/kernel/projects...h-4.1.5-rt5.patch.gz
tar -xpf linux-4.1.5.tar.xz
gunzip patch-4.1.5-rt5.patch.gz
cp patch-4.1.5-rt5.patch linux-4.1.5
cd linux-4.1.5
cat patch-4.1.5-rt5.patch | patch -p1
make xconfig
make
sudo make modules_install
sudo make install


Note that isolcpus will typically make Preempt-RT latency worse, idle=poll may help
Last edit: 20 Sep 2015 20:05 by PCW. Reason: wrap in link

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