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Old May 31st 04, 08:16 PM
Dimitris
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"guym" wrote in message ...
The system temperature is measured on the Northbridge with a VAXP. My sys
temp always runs lower than the CPU temp. I can't understand how the sys
temp could be higher. Use that as a relative temp and if it starts to get
unstable or averages higher over time, then I would be concerned.


It depends on which is your cpu, and how good the cpu fan is. A better
fan removes the heat from the cpu and spread it to other components in
the system, and the northbridge is the most likely to be affected, and
the one getting the biggest portion of that heat.

To clear it up i will speak with concrete numbers and give a more
detailed analysis. Say that your CPU temp is about 48C.. This means
that the air above the cpu fan has, on average, somewhat lower
temperature than 48(say 45), and the air after passing through the cpu
heatsink about equals that of the cpu(48C). Now because of the big
airflow that the cpu fan induces, this 48C temp air will dominate the
area above the northbridge fan. Now the amount of heat per second
removed from the northbridge chip is proportional to the temp
difference of the air above and under the fan, and proportional to the
quantity of air that passes through, per second. Since the latter
quantity is small(cause of the small northbridge fan) we can say that
almost solely depend on the temperature difference.. Since the temp is
48C above the northbridge fan, after blowing and passing through the
northbridge heatsink, the air temperature goes a bit higher than
48C(How much higher depends on the quantity of airflow/sec that passes
through, hence on the fan size,rotation speed e.t.c). But the
temperature of air that leaves the northbridge heatsink(which is as
explained before a bit higher than 48C) about equals that of the
northbridge chip. Hence the temp of the northbridge chip is a bit
higher than 48Ci.e a bit higher than cpu temp.

Now where this analysis goes wrong in your case so that you always
have lower system temperature. Simply you must have better ventilation
in the case so that most of the hot air from cpu goes outside and
doesnt dominate the area above the northbridge fan.