Maximum simultaneous keypresses on a keyboard?

invalid@example.com (Ogewo), Ogewo
Fri, 28 Aug 2020 23:07:09 +0000
Keyboards

I get an annoying beep of defiance whenever I'm in CS:S or any game and attempt to hold down a 4th key on my keyboard. The comand is not sent either. I read that USB keyboards have a max keypress limit of 6 and PS/2 is 10-20. Does anyone here know the truth? What can be done?

On a side note, are there any other performance advantages of certain keyboards in games, other than key layout?

Thanks