G5 Quad halting after 'over temp'

[Rob Ballantyne]

Hi All,

  I've just purchased G5 Quad to run FreeBSD PPC.  During install the
machine would throw a couple of errors (I couldn't capture them --
only on the screen) complaining about a lock reversal.  Shortly after
this the machine to complain that a couple of diode temps were too
high (~1000 C, I'm sure this can't possibly be true).

  I found some advice about an Xserve behaving similarly and the
suggest was to use sysctl to set machdep.manage_fans=0 (disable that
feature I presume).  I tried this and was able to install.  I do have
a question about the safety of this.  I presume this disables kernel
management of the fans.  If the kernel is not managing the fan speed
does this fall to the firmware?  Will the firmware keep the temps
within reason?

  Thanks,

Rob