The feature you are talking about is called n-key rollover. Cheap keyboards generally don't have it. Similar to you, I discovered the issue in the 90s with FPS games.
Keyboard manufacturers have been designed with n-key rollover as a feature since the late 70s, believe it or not. Keyboard technology has, in many ways, regressed since then. Fortunately, good keyboards are finally being made again—they just need to work on appearance and decent layouts again.
Keyboard manufacturers have been designed with n-key rollover as a feature since the late 70s, believe it or not. Keyboard technology has, in many ways, regressed since then. Fortunately, good keyboards are finally being made again—they just need to work on appearance and decent layouts again.