The current mad scientist project is to be able to log readings from the lm_sensors package on beowulf nodes (1Ghz Athlons). Having got the sensors package installed and put together a little script to be run from snmpd I've been using nrg to graph the results.
When I was running some benchmarks I checked the graphs to see what was happening and noticed that those Athlons do tend to light up when you do cpu intensive stuff.
The first peak (up to ~ load 2.5) is the node running bonnie++ to get some disk stats, when I saw the temperature was rising I decided to see how hot it would go, the second, longer peak is a bunch of sequential kernel compiles