How would I test that?

I only use it for travel and watching movies. There as a short "brain freeze" when plugging it in, but it continues to work normally.

The hardest part was finding a USB charger that:

- has decent wattage

- is not expensive

- also charges non-c USB

- does not explode (and bring down the whole trains outlets...)

- throttles/splits current (instead of running hot, shutting down and leaving your equipment uncharged for the night...)

I settled on this one: https://www.amazon.de/gp/product/B07PR8LDGL/ref=ppx_yo_dt_b_...

Only downside: no qualcom quickcharge 3.0 for the non-c USBs

>How would I test that?

On windows you can use CPU-Z, on linux look up for some command line solution.

I'm on windows :)

Didn't do heavy load testing, but see the same ~2800mhz on AC/battery/usb-c (it's an i5-6300HQ)

Throttling got better with every revision of the XPS 15 that I had. On 9550 it was abysmal - sudden downclocks to 800 Mhz, mouse cursor starting to lag and making the laptop unusable. On 9560 it got mostly fine, with occasional downclocks to 800 Mhz, but much less frequent. With my current 9570 it's all good, I can use it on any charger starting from 45 watts and it's working fine.