@wolf480pl There is no such thing as a "square wave", as that would require infinite bandwidth, there are only approximations.

The colder something is, the less resistance it has and therefore hardware becomes much better at signalling and you can push it much harder before it loses "clock lock".

This isn't really related, but some GSM towers used LN₂ cooling (not sure if just test towers), as that would allow the weakest, most feeble signals to be received from mobile devices.