I would expect that any motherboard that went to the trouble of including a PS/2 port would handle it with a real hardware interrupt, because the whole point of still having those things is to avoid the latency overhead of USB.
there are loads of things in the gamer space that are just branding BS… i could definitely see dodgy (or honestly even reputable) motherboard manufacturers adding PS/2 ports that are just basically a USB dongle built into the board and adding $40 for the dubious privilege
I would expect that any motherboard that went to the trouble of including a PS/2 port would handle it with a real hardware interrupt, because the whole point of still having those things is to avoid the latency overhead of USB.
Largely an urban legend. The internal electronics of the keyboard/mouse matter more than the protocol for end to end latency.
There are USB keyboards that beat a PS/2 one, at just 125 Hz polling. 1000 Hz polling pulls ahead even more.
https://www.youtube.com/watch?v=eEswl6kZq5k&t=650
But honestly, 1000 Hz polling is just for bigger numbers game. Even 300 ms are barely noticeable by humans, not to mention 10 ms of 100 Hz.
there are loads of things in the gamer space that are just branding BS… i could definitely see dodgy (or honestly even reputable) motherboard manufacturers adding PS/2 ports that are just basically a USB dongle built into the board and adding $40 for the dubious privilege