RPI4 Raspbian 64 bit & LinuxCNC

I use it on a hobby plasma table.

This guy uses one on a mill:

Taking into account the recent update (24/8/2020) of the RaspiOS_arm64,

RaspioOS_64

I redone the Raspbian 64bit RT-Preempt kernel (vers. 5.4.61_rt37) downloadable to this link

64bit RT-Preempt kernel (vers. 5.4.61_rt37

and also the arm64 versions of LinuxCNC (2.8.0 e 2.9.0pre0) downloadable at this link.

LinuxCNC 2.8.0 arm64

LinuxCNC 2.9.0.pre0 arm64

For installation the instructions are the same as those in the my first message of this thread.

Hi elovalvo,
thanks a lot for your work! I tried your release from today morning.

Without any glxgears running it look quite good (still not so good as phillc54's):


But as soon as I start 10 glx gears it look much worse:


I installed according to your description
Linux raspberrypi 5.4.61-rt37-v8+ #1 SMP PREEMPT_RT Wed Sep 9 18:58:22 CEST 2020 aarch64 GNU/Linux

cat /boot/cmdline.txt
console=serial0,115200 console=tty1 root=PARTUUID=60687991-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait quiet splash plymouth.ignore-serial-consoles processor.max_cstate=1 isolcpus=2,3

any ideas?

knirps wrote: any ideas?

Yes, that is still very good latency.

knirps wrote: Hi elovalvo,
thanks a lot for your work! I tried your release from today morning.

Without any glxgears running it look quite good (still not so good as phillc54's):

But as soon as I start 10 glx gears it look much worse:

This is mine with 10 Glxgears after a couple of days. It had a couple of odd spikes but perfectly adequate for my machine which has a Mesa 7i96 and a 2mS servo thread.

This using the ISO from the LinuxCNC website without any modification:
www.linuxcnc.org/iso/

It has isolcpus=3 in /boot/cmcline.txt

Anyone have latency test results with the above 64b kernel with a browser open and playing back a youtube video?

We found that the integrated GPU is the real time killer. We might try using a USB GPU and see how it effects the jitter.