After all, the Arduino isn’t actually measuring the CPU speed, nor is it directly controlling it (that’s still done by the original Turbo button wiring). But the truth is, even back in the day ...

If you’ve scavenged some random keypads and want to reuse them in a project without the hassle of figuring out the pinouts, then [Cliff Biffle] has an interface module for you. The Keypad Go ...