[Bug 209202] [PATCH] [powermac_thermal] In-Kernel PowerMac fan control does not effectively regulate some quad core models

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=209202

--- Comment #4 from Mark Millard <markmi at dsl-only.net> ---
(In reply to gmbroome from comment #3)

Do not interpret my notes as an attempt to block the changes. The notes are
just general background. Keeping a failure-mode machine operational can be
worth while in the right kind of context. I just did not want the performance
tradeoff and I did not want to ask Justin Hibbits to do more than he already
had done.

I have access to an example "quad core Powermac G5" of each type relative to
one pump vs. two, where both work without overheating problems and always have:

# sysctl -a | grep pump
dev.smu.0.fans.cpu_a_pump.rpm: 1716
dev.smu.0.fans.cpu_a_pump.maxrpm: 3600
dev.smu.0.fans.cpu_a_pump.minrpm: 1250

(So only one pump.)

$ sysctl -a | grep pump
dev.smu.0.fans.cpu_b_pump.rpm: 1485
dev.smu.0.fans.cpu_b_pump.maxrpm: 3600
dev.smu.0.fans.cpu_b_pump.minrpm: 1250
dev.smu.0.fans.cpu_a_pump.rpm: 1480
dev.smu.0.fans.cpu_a_pump.maxrpm: 3600
dev.smu.0.fans.cpu_a_pump.minrpm: 1250

(So two pumps.)

I put the same kinds of loads on each, although one has 12 GBytes of RAM and
the other has 16 GBytes.

As far as I can tell if a PowerMac G5 Quad Core has an overheating problem then
something is in a failure mode, usually the cooling system.

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