Currently, fancontrol allows a fan to be controlled by one sensor only. This
may, however, not always be enough. When testing, I am easily able to create
a temperature difference between Athlon 64 "Brisbane" cores exceeding 20 °C,
and it seems likely that larger differences are possible, as well. It is
also possible for a fan to be set up to cool more than one chip, which would
greatly increase the possible temperature difference even further.

It would be nice if fancontrol allowed a fan to be controlled by more than
one sensor - it could calculate the fan speed based on a reading of each
sensor in a group and choose the greatest value.