PowerMac G5 fans going crazy

[Julio Merino]

Hi,

I have this liquid-cooled dual G5 PowerMac sitting in my cold garage. The
machine runs fine for a while and can even do a buildworld in silence...
but sometimes, pretty much at random, decides to spin up its fans to the
maximum. The machine is pretty much idle when this happens so usage doesn't
explain this.

I haven't correlated this fully, but when the machine does this, it seems
to also become unresponsive. Moving the mouse on the console shows the
pointer moving but it eventually freezes. Except... the machine responds to
pings, and even to SSH. *However*, it is sluggish. SSH takes forever to
respond, but eventually does. Similarly, the console eventually recovers
too and allows input... until things become slow again. And while it's
responding, running "top" doesn't show anything strange, not in user CPU
consumption nor in sys.

Interestingly, running a "sysctl -a" makes the fans quiet down, maybe for a
long time, maybe for a couple of minutes only. See the diff below of
"sysctl -a" from while the fans are full-speed to right after, and notice
that the temperatures look just fine.

Any ideas about what might be happening here?

Thanks!


@@ -1,7 +1,9 @@
-dev.smusat.0.cpu_a1_core_current: 10
+device smu
+kern.consmute: 0
+dev.smusat.0.cpu_a1_core_current: 11
 dev.smusat.0.cpu_a0_core_current: 10
-dev.smusat.0.cpu_a1_diode_temp: 27.7C
-dev.smusat.0.cpu_a0_diode_temp: 26.5C
+dev.smusat.0.cpu_a1_diode_temp: 28.1C
+dev.smusat.0.cpu_a0_diode_temp: 26.7C
 dev.smusat.0.cpu_a1_vcore: 1
 dev.smusat.0.cpu_a0_vcore: 1
 dev.smusat.0.%parent: iicbus2
@@ -12,25 +14,25 @@
 dev.smusat.%parent:
 dev.smu.0.server_mode: 0
 dev.smu.0.sensors.slots_power: 16816
-dev.smu.0.fans.expansion_slots_intake.rpm: 4487
+dev.smu.0.fans.expansion_slots_intake.rpm: 1572
 dev.smu.0.fans.expansion_slots_intake.maxrpm: 4500
 dev.smu.0.fans.expansion_slots_intake.minrpm: 1560
-dev.smu.0.fans.cpu_b_exhaust.rpm: 3168
+dev.smu.0.fans.cpu_b_exhaust.rpm: 551
 dev.smu.0.fans.cpu_b_exhaust.maxrpm: 3200
 dev.smu.0.fans.cpu_b_exhaust.minrpm: 500
-dev.smu.0.fans.cpu_a_exhaust.rpm: 3031
+dev.smu.0.fans.cpu_a_exhaust.rpm: 548
 dev.smu.0.fans.cpu_a_exhaust.maxrpm: 3200
 dev.smu.0.fans.cpu_a_exhaust.minrpm: 500
-dev.smu.0.fans.cpu_b_intake.rpm: 3045
+dev.smu.0.fans.cpu_b_intake.rpm: 534
 dev.smu.0.fans.cpu_b_intake.maxrpm: 3200
 dev.smu.0.fans.cpu_b_intake.minrpm: 485
-dev.smu.0.fans.cpu_a_intake.rpm: 3173
+dev.smu.0.fans.cpu_a_intake.rpm: 538
 dev.smu.0.fans.cpu_a_intake.maxrpm: 3200
 dev.smu.0.fans.cpu_a_intake.minrpm: 485
-dev.smu.0.fans.backside.rpm: 2851
+dev.smu.0.fans.backside.rpm: 1174
 dev.smu.0.fans.backside.maxrpm: 3000
 dev.smu.0.fans.backside.minrpm: 1100
-dev.smu.0.fans.drive_bay_a_intake.rpm: 3792
+dev.smu.0.fans.drive_bay_a_intake.rpm: 1011
 dev.smu.0.fans.drive_bay_a_intake.maxrpm: 4000
 dev.smu.0.fans.drive_bay_a_intake.minrpm: 1000
 dev.smu.0.%parent: ofwbus0

-- 
jmmv.dev