Logitech K520 keyboard not responding on certain keystrokes

Solution 1:

This is due to the hardware. The Logitech K520 is a 2-Key Rollover (2KRO) keyboard. A 2KRO keyboard will be capable of registering at minimum 2 keys at the same time, but also some 3 key combinations, otherwise Ctrl + Alt + Del wouldn't work, but certain combinations will be limited to 2 simultaneous keypresses.

I have found these key combinations do not work with the Logitech K520
SHIFT + I + N
SHIFT + D + N
SHIFT + H + N
SHIFT + * + N
SHIFT + ~ + N
SHIFT + ~ + W
SHIFT + C + W

Most of those key combinations don't matter that much, but when typing: "SELECT DISTINCT" or "SELECT INTO" at speed it is very likely that you will press SHIFT + I + N at the same time as you usually press the 3rd key before you have had time to release the 2nd key when typing fast.

What is rollover?
Rollover is simply how well your keyboard can correctly register multiple keys being pressed simultaneously.

Not all keyboards are created equal when it comes to rollover. Where one keyboard might be able to handle half a dozen or more inputs, others might struggle to correctly recognise three keys pressed simultaneously.

Rollover is quantified as n-key rollover, where n is the minimum number of keys that can be correctly registered when pressed simultaneously. This is often written in its short form KRO. For example, 2–key rollover becomes 2KRO. Many inexpensive keyboards have only 2KRO, while higher-end keyboards (and many mechanical keyboards) have 6KRO or higher. If a keyboard can register all of its keys being pressed simultaneously, then this is called NKRO.
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