Hi Peter,

I am guessing that "uctlr" means µ-Controller, and yes, even then. The problem is not the clock frequency, it's the rise time of the pulse. There are a couple of things you can do to give yourself a decent chance of having a working circuit. First, keep the leads as short as possible. When the transmission distance is long enough that signal propogation from source to load takes longer than the rise time, you get weird reflection phenomenon. The other thing you can do is to use wires of suffieicent diameter to fit as tight as possible in the friction sockets. This minimizes the capacitance of the connection, and the corresponding phase shifting. There are other problems you can run into, but these two are the first that come to my mind and are easy to ameliorate. And the good news is that if you get a circuit working on the breadboard, it will almost certainly work in PCB form.