As work on the Spikeputor continues, I wanted to check out the shape of the clock pulses, now that a single signal feeds into 112 inputs (7 registers * 16 bits per register). In the entire design, there will be upwards of 165 clock inputs. The result of such a high fan-out number was not entirely unexpected:

At 37 µS for full rise, that starts rivaling the top speed I want to be able to run the processor (~40 µS, preferably faster if I can speed up the ALU). All of those tiny capacitances of each of the input transistors are starting to add up, slowing down the rise time! Luckily, there's a simple solution to this expected problem: build a clock tree. I inserted a buffer (two transistors) in front of every group of 16-bit inputs, and now the rise time is seven times faster. Math and physics works! Yay!

None of this is rocket science, but it's a very helpful and educational illustration of these principles. Onward!