I remember doing this too, it unlocked the multiplier which they locked at the factory by slicing through some metal blocks with a laser. My Duron 600 would run at 800 with a normal cooler & fan, then I added a really loud Delta fan and a copper heatsink and it was stable at a magical 1Ghz. Eventually I got cocky enough to solder a resistor between a certain pin on the motherboard and earth which effectively increased all the voltage settings in the BIOS so I could push enough voltage through it to run at 1.2Ghz - it ran like this for years as my only PC. Good times :)
Seems to have been a fairly common trick with the Durons. I sadly never experienced the rush of trying it mostly because Athlons and PIIIs were all I'd ever played with when the 1ghz chips started coming out, but this was probably what made the Durons so attractive to student hackers. https://arstechnica.com/civis/viewtopic.php?f=8&t=840954
Tangent: I love that I can pull up forum threads from two decades ago.
Ah! Athlons.
My overclocking journey picked up when I built a DIY watercooler out of a bent 5mm cooper sheet (at which thickness you stop calling it "sheet"?) polished to a mirror finish.
At some point, during the peak of easter european winter I kept the heat exchanger outside in the -20*C temperatures!
