Clocking in: creating a homebrew computer’s pulse

At the heart of every computer is a clock beating out the measure to which the machine keeps time.

Every computer needs a clock. At least one. But it doesn’t tell the time. It is more like a heartbeat, or perhaps a drum beat, to which important parts of the device synchronise their activities.

In a previous article on address decoding for the Zolatron homebrew computer, I talked about ‘qualifying’ or ‘gating’ signals through the cunning use of NAND gates and the clock signal. But I was getting a little ahead of myself because I’d said nothing about where that signal comes from. It’s both very simple and (sometimes) not quite as simple as you might think. So let’s get into it.