wrote:
Part 2 (shorter video 3 mins and 30 secs and looks at visualizations only, on both cores, since driver might run on different core):

Better analysis of PS/2 vs USB Keyboard, USB mouse show too (on dual core system).

https://youtu.be/Tv6e75GBfHI

Each pixel roughly represents one microsecond of time or so. Each black pixel shows something else consuming CPU, which in this case would mean USB drivers. It's possible that driver runs on different core, so both cores visualize.

Each visualization runs on it's own core.

It seems the PS/2 keyboard runs more consistent and consumes slightly less time than USB keyboard.

USB mouse uses a lot of CPU.

My Logitech mouse has adjustable ("update"?) rate, depending on
how much CPU power you want to dedicate to it. I assume they
could easily add that feature to keyboards too if they wanted to.
So far, I haven't ever tried a wireless mouse where I didn't feel
"lag", but I haven't tested alot, and none lately. I assume a
wireless keyboard would disappoint in the same way.