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ddc
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PostPosted: Mon Apr 16, 2007 9:05 pm    Post subject: ppc 7410 max temperature Reply with quote

hi,
DAYSTAR makes a kit to replace the a ppc750-400Mhz with a ppc7410-433Mhz
i know this kit is available for the apple powerbook lombard
(the kit makes the machine only 10% faster, but it adds the ALTIVEC features)

ppc750 and ppc7410 are able to report the temperature inside their die, on linux you can easily cat /proc/cpuinfo to see the cpu-die-temperature

i don't know the right temperature range ... and personally i experienced a damage caused of too hot temperature

so i coded a little easy script that shotdown the machine in case the temperature goes over a max value

has somebody experienced this kit, if so what is the average temperature he read ?


Code:

tempmax=`cat /etc/mytemperature-guard`
echo "   max temperature = $tempmax C"
while [ 1 ];
      do
        temp=`mysystem-info temperature`
        range=`mystringcompare $temp $tempmax`
        echo "temperature = $temp" > /dev/tty10
        if [ "$range" == ">" ];
           then
               echo "too hot"
               echo "too hot, halting the system" > /var/system-report.txt
               mybasta # it is a kinf of shutdown -h now
           fi
        sleep 4
      done;
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JoseJX
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PostPosted: Wed Apr 18, 2007 2:31 am    Post subject: Reply with quote

The temp sensors on the G4 are quite inaccurate. I wouldn't expect reasonable values from it. Besides that, I can't really tell you, sorry.
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ddc
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PostPosted: Wed Apr 18, 2007 5:32 pm    Post subject: Reply with quote

to be honest about the temperature, freescale has removed temperature sensor in the last G4 cpu, cause sensors on ppc750 and first 74xx (for example the 7410) are not calibrated and inaccurate

ok, they are bad, but sensors don't produce random number, they are right in +- 2C (and quite linear) so if you read a value of 40C, the real temperature is between 38C and 42C

no problem, the safe-temperature-program could be set to use the maximal critical value as it is able to shut down in a few second


on my measures

the ppc750-400Mhz has an average of 40C+-2C and should be guarded for temperature over 60C

the ppc7410-433Mhz has an average of 35C+-2C and should be guarded for temperature over 50C


could someone confirm these values ? (they are depending of the cpu usage, ram, etc, but the average can't be so different)

see your cat /proc/cpuinfo : it should report the cpu (die) temperature
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JoseJX
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PostPosted: Wed Apr 18, 2007 6:08 pm    Post subject: Reply with quote

My current G4 does not have a sensor. My old PowerBook G4 500 (7400) would see temps between 40C and 80C. It wasn't accurate enough that I'd trust it for anything.
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ddc
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PostPosted: Wed Apr 18, 2007 9:24 pm    Post subject: Reply with quote

JoseJX wrote:
My current G4 does not have a sensor. My old PowerBook G4 500 (7400) would see temps between 40C and 80C. It wasn't accurate enough that I'd trust it for anything.


DAYSTAR techs say 80C is too hot
i can say that my previous cpu ppc7410-433Mhz was working at 80C (and it was for 2 non stop days, emerging a lot) when it suddenly died ! The ambient temperature was 20C, The max temperature i read was 80C, and 80C is too hot: the machine should be
1) cooled more to reduce the temperature (see termaltake collerpad data sheet)
2) made shutdown -h now if it is impossible to reduce the temperature and the damage probability


about the accurate: i repeat, sensors don't think cat /dev/random, no, you have to consider the power is function (cpu usage~=number of switching transistors) so it is not a static value

freescale reports the measure is no accurate because the die sensors are
1) not linear (temperature to voltage translation goes in exponential way, and could be approximated linear only in the beginning range 0C..40C, the more temperature grows, the more values are not accurate ...)
2) in the linear range, values are precise in the+ o - 3C, out of the linear range the precision is a not constant function


the safe-guard-daemon has the goal to make your powerbook usage safe about temperature:
it could get this goal with 3 methods
1) brutally calling sync_&_poweroff
2) invoking shutdown -h now
3) invoking the pmud - sleep method

in the sleep state, the temperature grows down to the ambient temperature, so the machine could be waked up later without loosing jobs, just delaying them ....



p.s.
my lombard ppc750-400Mhz has been running 6 non stop days emerging all the gentoo system + my things
1) the average temperature is 40C
2) the max temperature is 60C


p.s.2
i will post about the use of a physical thermometer to calibrate the temperature: please note in this case i calibrate the temperature on the heat sink not from the internal cpu die. This produce s an offset between what it's read from the cpu and what is's read from the heat sink; cause the 2 temperatures are read with two different sensors (different technology, different temperature to voltage conversion) but in the range of linearity they will follow the same linear law.

p.s.3
the temperature measures are classified with a measure of the cpu usage (something like what is reported by the "top program"). This is important cause temperature depends by the number of transistors physically in use.
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ddc
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PostPosted: Wed Apr 18, 2007 9:31 pm    Post subject: Reply with quote

yes, 750,7400, 7410 have the temperature sensor, while the the last 74xx ppc has not
simply removed by freescale
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