powerbook doubles as a frying pan

hi,

the only time i ever noticed the fan on my powerbook turn on was when i could smell something
burning... it was while i was running a long-running java program which was cpu-bound. the program
was probably going for about a half hour.

i shut the machine down as soon as i realized where the smell was coming from. after that it
wouldn't boot. the tech says the ethernet chip had a "blister" on it. replacing the logic board
cost almost $600.

is everyone *totally* sure that activating the fan is entirely handled in hardware? is there no
register for controlling the threshold?

/proc/cpuinfo does not report the temperature (i'm not sure the hardware can report it).

for now, i put it to sleep whenever it gets hot. i suppose i should put sleep statements in
anything that is cpu bound to save the machine. also i pull out the pc card if it's not in use to
help with ventilation.

(what a day i'm having... i just got it back and spent the day trying to find out why java would
not run. after examing working- and non-working-strace's i noticed that the date was set to 1904.
the java vm will not initialize with a date like that. maybe it's because sun realizes that no
java machine was known to be working in the year 1904.)

--
Brad
brad@turbolinux.com      http://www.turbolinux.com/~brad/


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is everyone *totally* sure that activating the fan is entirely handled in
hardware? is there no
register for controlling the threshold?

I've seen nothing in Apple's own Darwin OS related to controlling the
powerbook fan neither. However, they do have code that use the CPU's
temperature sensors to control the ICTC (instruction cache throttling).

Troy have some code that allow to read the temp from /proc. However, it
looks like a lot of CPUs are so badly calibrated that the information
returned is almost useless... Maybe that's not the case in CPUs used in
portables, that's the case in some of the G4s used in dual G4s.

/proc/cpuinfo does not report the temperature (i'm not sure the hardware
can report it).

for now, i put it to sleep whenever it gets hot. i suppose i should put
sleep statements in
anything that is cpu bound to save the machine. also i pull out the pc
card if it's not in use to
help with ventilation.

(what a day i'm having... i just got it back and spent the day trying to
find out why java would
not run. after examing working- and non-working-strace's i noticed that
the date was set to 1904.
the java vm will not initialize with a date like that. maybe it's because
sun realizes that no
java machine was known to be working in the year 1904.)

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quoted

is everyone *totally* sure that activating the fan is entirely handled in
hardware? is there no
register for controlling the threshold?

I've seen nothing in Apple's own Darwin OS related to controlling the
powerbook fan neither. However, they do have code that use the CPU's
temperature sensors to control the ICTC (instruction cache throttling).

Which would be not-so-useful to control the temperature of the ethernet
chip, right? The PowerPC CPU isn't the primary source of heat in a laptop.
At least not to the extend the Intel CPU would be.
CPU temperature monitoring wouldn't be too useful either - the CPU
core always runs a lot hotter than the rest of the motherboard.

But I'm mostly guessing here - has anybody stuck a couple of temperature
probes on a PB motherboard and really measured the operating temperature?
What would the best 'hot spots' be for such an experiment?

	Michael


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At 12:01 PM +0100 1/29/01, Benjamin Herrenschmidt wrote:

Troy have some code that allow to read the temp from /proc. However, it
looks like a lot of CPUs are so badly calibrated that the information
returned is almost useless... Maybe that's not the case in CPUs used in
portables, that's the case in some of the G4s used in dual G4s.

G3s generally have a useful temperature sensor, but you have to know
the correction formula specific to the die revision you're using.
The raw data is not good for much other than deltas (i.e. if the raw
value changes by 12 C, you know that it really did change by about 12
C, even if you don't know what the real starting and ending temps
were).

However, from what I've heard the G4 sensor is essentially useless.
On my own dual processor 500, a MacOS temperature readout utility
consistently tells me that one processor is 24 degC (or more) cooler
than the other.  Both CPUs are the same die revision of course.
There is just no way for this to be correct; the CPUs are thermally
coupled by a nice thick chunk of aluminum (1" x 0.5" cross section at
least), due to the design of the heatsink.  Both are getting good
contact (I checked).

   Tim Seufert

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However, from what I've heard the G4 sensor is essentially useless.
On my own dual processor 500, a MacOS temperature readout utility
consistently tells me that one processor is 24 degC (or more) cooler
than the other.  Both CPUs are the same die revision of course.

	Maybe one is being used more than the other.  :)  That would often be
the case.
	I'm not sure if you guys discussed this, but I have two points on the
temperature issue.
	One is that the Wallstreet II series had a revision that had a
motherboard bus somewhere around 83 MHz and was way hotter than the
rest, which were often at 66 MHz.  I'm pretty sure the cpu speed was
292 MHz on that faster motherboard.  They had to lower the motherboard
bus for subsequent models because it was too hot.
	The second point is that I heard that about 1 week before Macworld
Expo, somebody checked in Macintosh power management code to Darwin's
CVS.  :)

=====
"Don't expect your own messiah; this neverworld which you desire is
only in your mind." -- http://www.dreamtheater.net/songb4.htm#IV5


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At 7:03 PM -0800 2/2/01, Dan Bethe wrote:

quoted

 However, from what I've heard the G4 sensor is essentially useless.
 On my own dual processor 500, a MacOS temperature readout utility
 consistently tells me that one processor is 24 degC (or more) cooler
 than the other.  Both CPUs are the same die revision of course.

Maybe one is being used more than the other.  :)  That would often be
the case.

The construction of the heatsink used in the dual processor G4s
guarantees that the two processors should always be about the same
temperature.  They're thermally coupled by a very thick chunk of
aluminum.

Besides, the difference between the readings remains the same whether
the machine is doing nothing or crunching RC5 full blast (the MacOS
RC5 client does use both CPUs).

One is that the Wallstreet II series had a revision that had a
motherboard bus somewhere around 83 MHz and was way hotter than the
rest, which were often at 66 MHz.  I'm pretty sure the cpu speed was
292 MHz on that faster motherboard.  They had to lower the motherboard
bus for subsequent models because it was too hot.

That was the original Wall Street series, not Wall Street II (which
was actually codenamed "PDQ" by the way).  The 233 MHz WS had a 66
MHz bus but the 250 and 292 MHz WS models had 83 MHz busses.

But the bus wasn't the reason they got so hot.  That was caused by
the use of first generation 0.29 micron Motorola G3 processors (all
that was available), and inadequate cooling.  Later versions of the
G3 were process shrunk and use a lower core voltage, resulting in
less than half the power consumption at the same clock.  And later
versions of the PowerBook G3 got better cooling technology.

   Tim Seufert

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The second point is that I heard that about 1 week before Macworld
Expo, somebody checked in Macintosh power management code to Darwin's
CVS.  :)

There have been bits of power management in Darwin CVS since public beta.
PB could put some (but not all) powerbooks to sleep, had temperature/ICTC
control, etc...

However, AFAIK, the current Darwin CVS lacks all the support for recent
machines. Looks like almost all of the "platform expert" code that
contains driver for the Apple custom ASICs have been removed from the
kernel tree (it's beeing moved to separate drivers) and didn't yet show
up in the IO tree.

Ben.


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