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

bugzilla-noreply at freebsd.org bugzilla-noreply at freebsd.org
Mon May 2 21:07:06 UTC 2016


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

--- Comment #3 from gmbroome at vcu.edu ---
(In reply to Mark Millard from comment #2)

The history on my work with this is that I grabbed two of these systems on the
cheap from "the Bay."

Both had the "revision 2" CPU assembly, and both worked fine w/ OS X, Linux,
and FreeBSD.

Six months on, one of the cooling pumps in a system died.  The only replacement
that I could get was a "revision 1" CPU assembly.  After doing the replacement,
both OS X and Linux continued to work fine (albeit with the same reduced
performance that you noted) but FreeBSD showed the precise behavior that you
described in the mailing list posts.

Through a series of CPU assembly swaps, and ordering a second r.1 purely for
the testing, I'm reasonably certain that the r.1 CPU assembly is, itself, the
culprit.  Though I certainly understand the notion that installing
known-defective hardware (why else would there have been a rev?) will cause
problems, it makes sense to go ahead and accommodate this r.1 CPU assembly in
the driver as the r.1 CPU assembly is the far more common replacement part
these days, and r.2 is getting very difficult to obtain, even if one has
bottomless pockets.  Based on my own testing, the provided patch allows the r.1
assemblies to work, and has a negligible impact on r.2 assemblies.

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