I7 7800x RT linux 64bit issue

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15 Mar 2018 14:58 #107376 by Hujtebesuka
Hi. Thanks all you for this forum
I installed many diferent lcnc livecd only new betta livecd 64bit rt worked out fine for me
I have 6 core cpu and lcnc seems to like 1 core cpus
Becouse i disable rest of 5 cores and Max Jitter base is from 6000 to 9000
If i got all 6 cores running linux its jumps up all way to 160000 is it just the way it is or can get it better on 6 cores by telling linux use dedicated core and leave other things on other cores ?
* uname -r *
Gives 4.9.0-6-rt-amd64
Works good nvidia gpu resolution 2560x1440@144hz
Just need help why lcnc no like 6 cores

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15 Mar 2018 16:25 #107379 by andypugh
How are you disabling cores?

You can use isolcpus to dedicate one core to realtime, but that might only work with RTAI.

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16 Mar 2018 06:23 - 16 Mar 2018 07:45 #107411 by Hujtebesuka
I can disable cores in bios motherboard lets me do this
I tryed isolcpus=1,2,3,4,5,6
Grub-update
No luck still high base jitter
# ps -aeF
Show that all processes run on core 0
But still jitter is same as when all running


Than i turn all cpus back on and

#echo 0 | sudo tee /sys/devices/system/cpu/cpu1/online#

And its say no such file or derictory so cpus not running in system

So i enable thrm back on in grub
Try disable cores manualy but thats freezes all sestem
Last edit: 16 Mar 2018 07:45 by Hujtebesuka.

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16 Mar 2018 13:41 #107425 by andypugh
I think that "isolCPUs = 6" (Maybe 5) will leave realtime running on the last CPU.

I don't think that ps or top can see processes on the isolated CPU.

But it is a while since I experimented with this.

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16 Mar 2018 14:11 - 16 Mar 2018 14:13 #107430 by PCW
Replied by PCW on topic I7 7800x RT linux 64bit issue
Do you intend to use a parallel port interface to your motion hardware?

If not, the 160 usec latency may not be very important.
Last edit: 16 Mar 2018 14:13 by PCW.

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16 Mar 2018 14:27 - 21 Mar 2018 20:02 #107431 by Hujtebesuka

Do you intend to use a parallel port interface to your motion hardware?

If not, the 160 usec latency may not be very important.


All i need it to control small 3040 china make cnc mill engraver its more for plastycs and acrylic cutting just want it work right and not miss steps

Disabling cores not to bad just wanted know if can make it not to use extra cores as my test show its more of matherboard and cpu combo fault i5 i had was warking fine out of a box

I used this livecd build only need Internet connection
And after desable cores so have 1 core
Base Jitter test very good 3000 - 8000 as far as i could test resolution ideal on 1080gtx
Just missing some drivers for wirless card sound card but not critical
When i try enable cores and get jitter base 60000 the router was making randoom sounds like if controll box broken just no go whit jitter base over 60000

Best livecd so far for me hope it will be in downloads install wiki save some time to look for that livecd on forum )
LIVECD 64bit
linuxcnc-stretch-uspace-amd64-r10.iso
Last edit: 21 Mar 2018 20:02 by Hujtebesuka.

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