> On 2020-10-02, at 3:14 PM, Eliot Miranda <eliot.miranda at gmail.com> wrote:
> 
> So two questions, a) is there a way from software or GUI to find out if the pi is throttling? b) is there a way from software or GUI to find out if the input voltage is dripping

There is existence proof of this in that the menubar has a widget (in Raspbian, at least) that shows the cpu temperature and changes color when it is throttling. I'm making a possibly naive assumption that it actually tells the truth.

> 
> oh, and c) how did you debug this?

Oh, the usual way; curse, swear, try ludicrous ideas that make no sense just moments later. Since I have two Pi4, one with an SSD and one without I was able to swap the SSD out and try the uSD to see if it was anything to do with that. I ran an eeprom state updater/checker (remember, unlike the earlier models the Pi 4 has a chunk of eeprom for the hardware boot code) and showed that they were claimed identical. I made sure to run the exact same vm/image on both. 

Eventually the Pi told me what the problem was itself - a widget I'd never seen before appeared saying 'voltage low. check your power supply'. Well, yes, there you go. I'd not previously considered that throttling was caused by anything other than temperature and was in the middle of writing a post to the Pi forums to ask why the problem Pi was indicating throttled when it was only at 30C, whereas the other was happy up to 50C with no throttling. Lesson learned.
Luckily I had another suitable PSU on my desk awaiting a case build for the other Pi 4 so I had one to swap in.

All in all, just like debugging an errant Cog. But swearier.


tim
--
tim Rowledge; tim at rowledge.org; http://www.rowledge.org/tim
Java:  the best argument for Smalltalk since C++