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Re: Off-Topic: G5 Open Firmware instability

On Fri, May 13, 2022 at 01:43:24PM -0400, Lennart Sorensen wrote:

> > Clearly there is. My concern however is that I have two issues and
> > the OF one is distinct from the cooling one. The machine can boot into 
> > the existing Linux (from SATA) and stay up indefinitely (if load av < 
> > 1.5) but from a cold boot, will hang in OF in under 1 minute.  Maybe 
> > Forth is a real resource hog :-)
> It is certainly not unusual for firmware to run on a single core at 100%
> (implementing idle handling and interrupts and such is just considered
> too much hassle for something that isn't normally going to run).
> So yeah it is actually not unlikely that openfirmware would cause the
> CPU to run hot compared to linux at low load.

This had occured to me. It is certainly likely that it's pinned to a
fixed cpu core.  Still it seems odd that it hangs so quickly.

This won't fix the OF issue but (as I mentioned in previous message)
I'll see if I can disable the 2 cpus that are running clearly hotter 
than the others in Linux and see what is then reported for the 
remaining two.

I may have to just bite the bullet and try and fix the cooling and 
hope it also fixes the OF issue.

Things like "setenv" no longer actually changing values from OF but
/usr/sbin/nvram changing them from Linux strike me as rather odd
manifestations of a cooling issue but hardware is funny stuff.


Tony Jones
SUSE Kernel Performance Team

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