How Accurate Are MBP Temperatures?

[Premal212]

I was just checking, intel power gadget and macs fan control and I'm not so sure about the temperatures.

Normally when running my CPU is around 66degrees, as soon as I run the yes command (100% CPU) the temperature shoots up to 99 degrees, within the matter of a second - that's not the issue.

I close the yes command and the temperature drop to 80 in a second and to around 70 a few seconds later. Even if the fans were maxed, which at the time they weren't, it would take around 10 seconds for that heat to dissipate.

It just feels a little fishy. I.e. I don't believe the temps can drop that fast when the fan isn't at max capacity. Logic would dictate that it would take some time for that level of drop.

I dont have istat pro anymore, but the temps are in line with macs fan control, so I can't imagine intels power gadget is cooking the books.

 

[1096bimu]

The temp drop isn't caused by the fan dissipating the heat, it's because the heat got out from the CPU.
At max load there is too much heat they get stuck very close to the CPU.

You would not have this behavior with a desktop computer with a water block directly on a delid CPU.

 

[Premal212]

The temp drop isn't caused by the fan dissipating the heat, it's because the heat got out from the CPU.
At max load there is too much heat they get stuck very close to the CPU.

You would not have this behavior with a desktop computer with a water block directly on a delid CPU.

Ah, so by virtue of that, my heatsinks should still be around that temp, but my CPU should have dropped as per the screenshot?

 

[1096bimu]

Ah, so by virtue of that, my heatsinks should still be around that temp, but my CPU should have dropped as per the screenshot?

Yes, when at full load there is a large temperature difference between the silicone and the heatsink. When heating stops, the temperatures quickly equalize across the thermal system. But it will be a while before the entire system gets cooled down by those tiny fans.

 

[Premal212]

Makes perfect sense ! Thanks

 

[maflynn]

I close the yes command and the temperature drop to 80 in a second and to around 70 a few seconds later. Even if the fans were maxed, which at the time they weren't, it would take around 10 seconds for that heat to dissipate.

Yep, that makes perfect sense, you're no longer doing a task that is pushing the CPU to 100% and jumping into turbo mode, so its not generating the heat. The MBP's thermal management is then able to bring the down fairly quickly

 

[Premal212]

Yep, that makes perfect sense, you're no longer doing a task that is pushing the CPU to 100% and jumping into turbo mode, so its not generating the heat. The MBP's thermal management is then able to bring the down fairly quickly

Makes sense. I didn’t think the sensor was within the CPU. I thought it was just closer towards the hinksink

 

[jerryk]

Makes sense. I didn’t think the sensor was within the CPU. I thought it was just closer towards the hinksink

Sensor is in the CPU package to throttle or shutdown CPU to prevent damaging the CPU.

This page goes into some of the details of Intel's thermal measurement and protection systems. https://www.intel.com/content/www/us/en/support/articles/000005597/processors.html