Critical temperature reached, shutting down

Wed Apr 20 10:22:14 UTC 2005

Is this supposed to be a sane default for AMD Duron/Athlon chips?

  Apr 20 11:44:04 rawhide kernel: Critical temperature reached (65 C), shutting down.
  Apr 20 11:44:04 rawhide shutdown: shutting down for system halt
  Apr 20 11:44:05 rawhide init: Switching to runlevel: 0

What's going wrong there in FC4T1 and T2 as opposed to FC3?

I can work around it by customising the trip_points in 
/proc/acpi/thermal_zone/THRM/ but why is such a non-trivial step
necessary?