Interesting temps and flows

Tom Brown · Post by **Tom Brown** » Tue Dec 02, 2003 2:47 pm

During a bunch of fan speed benchmarks I was doing on my desktop, I found that the MB temp went up by two degrees when the CPU fan is at it's highest setting on my Rheobus.

The CPU cools better the faster I run the CPU fan but at it's max setting, the MB temp pops up two degrees, despite not having touched the case fan speed. When the L1A on the CPU fan down is <= 10 volts, the MB temp is constant.

lenny · Post by **lenny** » Tue Dec 02, 2003 3:23 pm

Any idea where is the case temp sensor? Maybe at higher fan setting the hot air from CPU HSF is being blown onto the case temp sensor, esp. if it's on the Northbridge.

Post by **Rusty075** » Tue Dec 02, 2003 3:24 pm

Tom, I can explain your odd readings.

The motherboard thermal sensor on the NF7 is between the CPU and the RAM. When the CPU fan speeds up, it blows more warm air towards that sensor.

ez2remember · Post by **ez2remember** » Tue Dec 02, 2003 3:42 pm

I generally don't trust case temp sensors because it doesn’t tell you how warm the air is inside your case. Put a probe inside the case and you get completely different reading. What it does tell you is the temp wherever the sensor is located. This is more or less useless for any kind of purpose.

A mean if you place a fan over the temperature sensor it would drop. Does this mean your cpu is running cooler from the supposedly cooler case temps? Nope.

As Lenny pointed out... It could be a number of things, your Antec 120mm fan may have been providing good airflow direction over the case temp sensor. However when you set your HSF to max, you may have tipped the fine balance of airflow. Now the hotter HSF airflow is blown over the sensor instead.

It's really weird how airflow works and more fans/increased airflow doesn't mean a cooler system. Good direction and channeling is key. Read Ralf's 1700cfm post...

Update: And as Rusty pointed out too.

I thought old timers suppose to be slow at typing? LOL