CPU clock maxed (but little load) when I play sound through external audio interface
 

Hi everyone. I started using Ubuntu 18.04 on my Dell 5491 which has i7-8850H CPU. Normally the CPU governor works well and CPU clock varies between 800MHz - ~4GHz. But whenever I start playing audio through my Behringer UMC404HD interface, the CPU clock goes way up and starts oscillating around 4GHz, however, no significant CPU load can be observed. This leads to rising core temps, fan speeds and power draw. Tried using a different USB port, and it's the same. The interface was working fine under Windows.

The increased clock effect cannot be observed with built-in audio.

I upgraded kernel to 5.0.5 in hopes that would resolve the issue, but no luck here. I set audio codec power management to ON using powertop, but that did not help either.

I'm not sure how to tackle the issue. Any pointers appreciated.

apparently playing sound through your behringer is very taxing on your CPU.

that doesn't mean it isn't there.
fans springing into action are a pretty sure sign.
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if trying some fix didn't help, undo it again.

for everything that you share with us, you also need to document it:
commands issued, output received etc.

I dug deeper and noticed that during playback, the xhci_hcd driver is causing > 10000 interrupts/sec. Is that normal?

you need to show us a little more than that.
how are you measuring interrupts?
what else do you notice when this behavior occurs?
system logs, dmesg etc.?
please read my previous post and the first link in my signature.

from what you wrote, all i can say that i also have that module active on my system.