Knez: Do you run only OS9 on your MDD?
Nope, I dual boot Tiger and Mac OS 9.2.2 on it and always have. I got my 1.8ghz MDX and the 1.6ghz MDX when they where dirt cheap and I didn't think much of it. They where more or less plentiful back then and could be had for $50 or so plus shipping, and I always thought I'd be able to replace it if I'd ever damage or destroy anything.
With todays prices I wouldn't even consider experimenting like I did way back then, all in the name of science of course. I slapped the copper heatsink on it back in 2017 or so and it have worked wonders since then, so I haven't had a reason to mess with it.
Just to give it some context, so I don't stand out as a raving lunatic