Mechanical keyboard jargon explained
With terms like N-key rollover, actuation, reset point and anti-ghosting technology, picking the right mechanical keyboard can get confusing. Here’s what everything means.
The point at which key input is registered, on all Cherry MX switches, this point is halfway down the switch.
The point at which the key resets and can be pressed again. Black and Red switches have matching actuation and reset points, making them the best for double-tapping. On Brown switches, the points are about 0.1mm apart, while Blue switches have a reset point about 0.75mm higher than the actuation point.
Linear Vs Tactile
Linear switches offer the same feel all the way through the key press, resulting in a smoother feel. Tactile switches have a noticeable bump halfway through to let you know you’ve activated the switch.
Key rollover refers to how many simultaneous key presses can be successfully processed. Only PS/2 keyboards are capable of true N-key rollover i.e. every key can be pressed simultaneously. This is because these keyboards are direct input, with each keystroke registering straight to the CPU. USB keyboards, on the other hand, are limited by the buffer size of the USB controller to just 6-key rollover, or up to 10-key when including modifiers. However, many companies have found ways to increase key rollover via USB. For example, by having the computer register multiple (sometimes as many as six) keyboards on the USB controller, ensuring multiple inputs are sent through simultaneously.
Polling refers to how often the CPU receives input from the keyboard. The higher the number, the more frequently information is sent. Only USB keyboards require polling (as PS/2 keyboards are direct input). Realistically, anything over 200Hz is unnecessary as input from a keyboard is limited by the time it takes for a key to reset.
Originally, ghosting referred to a phenomenon where certain combinations of simultaneous key presses could result in additional ‘ghost’ inputs being registered. With modern keyboards, this rarely (if ever) happens anymore, and now, anti-ghosting generally refers to technology used to prevent dropped inputs from occurring on keyboards without full N-key rollover.