Latency spikes on Dell Optiplex 7060 (i5 8500/32GB Ram, Radeon R5 430)

Short answer = use the built in graphics
Long answer = most AMD cards work with open source drivers that come with Linux, i have several RX580/8GB and had RX6700XT, RX6800XT, RX6900XT and all worked fine, but none of them work with proprietary AMD drivers as the Real Time kernel does not like the proprietary drivers.
I did say "most", some older ones will not work no matter what.
And in general NVIDIA is worse, with open source and proprietary drivers.
Very old Matrox cards were good, but those were AGP, not PCI-E.

zmrdko wrote:

Is there any hack how to tackle with radeons?

GRUB_CMDLINE_LINUX_DEFAULT="quiet isolcpus=4,5 radeon.dpm=0"
GRUB_CMDLINE_LINUX_DEFAULT="quiet isolcpus=4,5 amdgpu.dpm=0"

Not sure which works...
 

well, this is so much better:
 
 

That looks very good, even for software stepping with parallel port.
Move on to making chips!

Can you please post this together with what you did here
forum.linuxcnc.org/18-computer/39371-res...or-use-with-linuxcnc
So it can be easily found.
Thank you.

I did fresh install again to verify and installing irqbalance was the thing that made all the difference.

I will post details as you asked.