Back in late 90s, I owned a computer store, and one less-than-kosher trick of the trade was to overclock a CPU. Some chips could run faster than there posted speeds, and many an geek would try to see how fast they could get a chip to safely run. For many years, I had a machine that had a Celeron 266MhZ overclocked to 400MhZ. It's not illegal in and of itself (selling a 200 overclocked to 300 as a 300 would be), but it throws the CPU warranty out the window.
Back in my computer days, the hardcore computer innards geek's site was Tom's Hardware Guide; they taught the fine art of changing the jumpers on the motherboard, hot-wiring CPUs designed to avoid overclocking (it became a cat-and-mouse game between Intel and the geeks), and adding heat sinks and cooling fans.
I haven't been back to Tom's in a while. Among a number of interesting things, here's a pictorial history of the CPU.