PowerMac G5 quad-core, CPU A1 DIODE TEMP: 90.8 C (for example): How to handle? [Mac OS X behavior]

[Justin Hibbits]

I noticed on my quad running OS X spins up the fans all the way down at
55C. Perhaps you can try that, set the initial multiplier to 300 or more.
I can add a sysctl to change the multiplier, if that would help people.

-Justin
On Jan 17, 2015 2:25 PM, "Mark Millard" <markmi at dsl-only.net> wrote:

> Looks like only Justin and Nathan got the graph (since I directly sent the
> message to them but the mail list stripped it).
>
> ===
> Mark Millard
> markmi T dsl-only.net
>
> On 2015-Jan-17, at 02:20 PM, Mark Millard <markmi at dsl-only.net> wrote:
>
> I've included a picture of the graph of core temperatures from Mac OS X,
> spanning a little over 6 minutes. The core temperature plots are colored
> non-black.
>
> The "5 to 7" that I mentioned below is more like "3 to 12" over this time
> interval.
>
>
>
>
> ===
> Mark Millard
> markmi at dsl-only.net
>
> On 2015-Jan-17, at 02:04 PM, Mark Millard <markmi at dsl-only.net> wrote:
>
> Mac OS X 10.5 does force idle time of some form to keep core temperatures
> down! My evidence is as follows.
>
> The application Temperature monitor does show me temperature records
> (including graphs over time) under Mac OS X 10.5 for the G5. (No rpms.) It
> displays the information as for cpu A 1&2 and cpu B 1&2 (instead of 0 and
> 1). A2 is what it shows as a the hot one, matching FreeBSD's a1. I watched
> with the current short-term temperature display updating once a second (set
> via preferences).
>
> Once it reached around the low 90C range on A2 the temperature on A2
> started oscillating, going from the mid/low 90C's down to the 60C's/70C's
> and back up again, over and over, fairly rapidly. But the graph of the
> temperatures for all the cores shows all the CPU/core temperatures as
> oscillating in matching timing.
>
> So I conclude that Mac OS X is doing something to give all the CPUs/cores
> time to cool down as soon as any one of them gets too hot.
>
> So I do not expect Mac OS X to automatically power down, it has already
> been far longer than it takes for FreeBSD to shutdown with the patched
> RPM/cooling code. Menu meters shows the cores as fully used (mostly 100%,
> occasional 99%). They are mostly running 6 of my double/long-long HINT
> benchmark variants built various ways with parameter values input that are
> designed for long runs. (HINT is memory/CPU limited until it causes
> noticeable paging. But I've configured to not page with the 16GB of RAM
> avilable.)
>
> So far the maximum temperature is 95.8C, and that is on A2. The next
> highest core is A1 at 81.2C so far. During this oscillation A2's minumum is
> 60.7C so far.
>
> There is a pattern to the drops: there is a sequence of 5 to 7 in a row
> where the drop starts back up almost immediately but then there is a longer
> duration with the temperatures staying down before it starts back up again.
> After the longer duration drop the temperature rise is not as rapid so it
> is longer until the next forced-drop.
>
> For the 5-7 in a row they tend to get somewhat closer together the further
> into the sequence. It may be that the time between triggers the longer
> cooling duration.
>
> The G5 has been kept busy for well over an hour, far longer than FreeBSD
> did for "make -j 8 buildworld buildkernel"
>
> ===
> Mark Millard
> markmi at dsl-only.net
>
> <ShortTermTempGraph.jpg>
>
>