so I ran into trouble with a new machine I built recently.

It appears to be that when I enable threadirqs or use an rt-Kernel, I am getting an xrun inferno.

At first everything is fine but after a few seconds/minutes of playback I get thousands of xruns.

I am on Manjaro (KDE),  the kernels I tried so far are

5.8.3-2 - working ok'ish without threadirqs enabled

5.6.19_rt12-3 - bad

5.4.59_rt36-1 - bad

The funny thing is that I had a nice running system at first (around two months ago) on the same machine, the xruns started suddenly out of the blue. (Kernel update?)

Configuration is

Ryzen 5 3600

B450 Aorus pro

Motu 1248 

Manjaro KDE

I tried to higher the buffers to 2048, didn't help.

I installed an USB2 PCIe card so that I could separate the usb audio interface from other stuff and prefer its IRQ with rtirq.

Nothing helped.

What could be wrong?

I would love to hear your opinions

Best regards 

Moshe Werner