Test Input Lag

Ideally for 60 FPS games, max input lag must be within 16.67ms (1/60)s.

MAME

1. Press F5 to pause the game
2. Assuming the character is facing left, press and hold right arrow key to make him face right
3. Press Shift+F5 while holding the right arrow key
4. Count how many Shift+F5 press it take for the character to face right. Each Shift+F5 key press advance the frame by one.
5. If it is none, then it’s perfect! No input lag!

Retroarch

1. Press P to pause the game
2. Assuming the character is facing left, press and hold right arrow key to make him face right
3. Press K while holding the right arrow key to advance by one frame.
4. Count how many k press it take for the character to face right. Each k key press advance the frame by one.
5. If it is none, then it’s perfect! No input lag!