For those who have difficulty visualising numbers, this graph might help a bit! Lord Vetinari's testing missed out a couple of voltages, so I've ended up interpolating them. The points that are interpolated are marked in red, so you can easily tell which figures are indicative and which figures were real.
I've also added a linear trend line. This is like drawing a straight line to be as close to the numbers as possible. It helps to show where the clock speed is starting to fall away from the trend.
Anyhow - here's the graph!