G5 Quad halting after 'over temp'

[Nathan Whitehorn]

On Feb 11, 2012, at 8:15 PM, Rob Ballantyne wrote:

> 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?

The thing it does on earlier G5s is that the firmware runs all cooling  
devices at maximum if they aren't set, which is probably not what you  
want but is unlikely to set your machine on fire. Could you send the  
output of dmesg and the output of sysctl for the various sensors,  
dev.smusat, and dev.smu?
-Nathan