Diagnosing CPU spikes

Hi! I have a fairly complex patch in MOD-UI and I’m getting occasional spikes to 100% CPU usage. Usually it’s around 70% and the CPU temp hovers around 64. I’m also getting a red warning symbol on my Zynthian screen. I suppose these are connected. The Zynthian Wiki doesn’t include pictures of the different warning flags, so I don’t know what the flag actually means. It’s a red triangle with an exclamation mark if I’m reading it correctly. Any idea what could be going on? My Zynthian is a hodgepodge I built half by accident, but maybe it’s a software issue.



I’m running four MIDI Channel Filters, four Dexed, four ChorusI, four ArgotLunars, a disabled 2x2 Gain, and Invada Stereo Phaser, a Calf Tape Sim, Reverb, Exciter and Bass Enhancer and an enabled 2x2 Gain.

That’s the XRUN flag.


Some thoughts:

  • If you aren’t using a Pi 4 yet, you need it.
  • Make sure you have a solid power supply. A weak one can cause all manner of problems.

Stupid question: What’s an XRUN?
Considering I’m using a power bank, PSU problems wouldn’t be very surprising. I really would like to get this working with a power bank, though, and it should be new and decent. I guess I should find a way to power the screen separately.

It basically means that the CPU can’t keep up with all that you’re trying to do. The “X” refers to both under- and over-runs. See this article for more.

OK, @zynthianers everywhere, has anyone else tried with a power bank? What’s the best one to use?

I still get the same spikes and flags with the official PSU that came with my Raspberry Pi 3B. Am I just asking too much? Any idea why they are random spikes instead of having anything to do with what I play? And why it would hover at 70% most of the time.

I also get spikes if disable every pedal and stop sending any MIDI to the device.The average CPU usage drops to around 64% with nothing going on.

I have similar issues with mod UI. I am going to look at my power options soon.

It looks like I’m not getting anymore spikes after getting rid of Calf Reverb and Tape Simulation. CPU usage is less than 50% now.