2008 MBP - fan always at minimum no matter CPU temp

[tony359]

Hi all,

I'm tinkering with an old MBP I've acquired. On another thread some of you guys helped me bringing it up and running with the OS. All is now good. Today I've cleaned the fans and heatsinks and I wanted to makes sure the system was ok under load. I downloaded "CPUTest" and istat menu. I realised that the fans would just stay at minimum all the time even though the CPU DIE temp was reacing 104 degrees celsius.
Following some online advice I reset the SMC. I could hear the fans spinning up and then down during the following boot, I suppose it's some sort of calibration. Fans would then react to temperature if I ran CPUTest during this cycle. However, once the fans eventually go back to minimum speed... they stay there no matter what I do with the MBP.

I've read many people complaining about high temps on MBP but nobody has ever mentioned 104 degrees celsius to be honest...

The fans work, the sensors seem to work. Is there something broken software-wise which Apple could not be bothered to fix?

Thank you all!

 

[tony359]

Ok, quick update. While tinkering with the machine I installed a game - I'm not a gamer, I was just curious. During the game the fans sped up to max power and temps were around 80 degrees.
So it seems that everything works as designed and that for Apple it's ok that the CPU die reaches 104 degrees if the GPU is not running as well?

 

[tony359]

Allow me to doubt Apple's expertise on this decision - the fan only slightly spins up around 108 degrees C. Madness.

BTW this is not a CPU test, this is an actual software rendering a video.

 

[Sanpete]

It should throttle before it gets that hot, regardless of fan speed. I don't know if it's possible to get around that, so I'd suspect a reporting error.

 

[tony359]

I didn’t check yesterday but I believe it does throttle - and that’s why it doesn’t rise any further than that.

 

[Sanpete]

Should throttle before it hits 100C.

 

[tony359]

how can you check if a CPU is throttling on a Mac? What software would you suggest?

Edit: I couldn't use Intel power gadget as it doesn't work on my CPU and I couldn't find an older version.

I then run pmset -g thermlog on terminal. The speed limit stayed at 100 despite CPU temperature reaching 108 degrees C...

 

[Sanpete]

Which is why I suspect a reporting error. But I don't know where the reports for the software you mention come from, or how to check them.

 

[tony359]

I'm just guessing: isn't the throttling 'decided' by the CPU itself? I mean, there's is no OS and no software involved I suppose.

 

[Sanpete]

As far as I know, the 100C limit isn't something that can be overridden by users, including with software written to help control throttling.

Speaking of which, I suppose it's possible something has changed or corrupted the fan speed control. I think that much can be controlled with software. But you should still get throttling soon enough to prevent 108.

 

[tony359]

Bear in mind that I have wiped the disk so if it’s software it’s either something that wrote into a firmware or it’s a firmware corruption? I don’t know, I feel it’s so unlikely!