How does CPU temperature correlate with fan speed ?

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How does CPU temperature correlate with fan speed ?

Hi,

I have the feeling that the battery issue in OS X 10.7 is directly correlated with the higher usage of the fans.

The fans speed up to 2400 rpm at approx. 53 degree celsius. At 60 degrees they run with 3100 rpms.

As far as I can remember this is far more than under SL and would automatically explain where the battery drain comes from.

How is the speed regulated ? Is there some readout ? Does anyone has some effective numbers from SL ?

Hardware:

MBP 6,2

Best,

Peter

P.S.

Forgot to mention, that I have already reset SMC a couple of times and the batteries are calibrated.

Message was edited by: BaedaBln

MBP, iMac

Posted on Aug 16, 2011 11:51 PM

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Answer 1

BaedaBln Author

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Aug 17, 2011 11:41 PM in response to BaedaBln

Some more numbers:

52 degree celsius 2100 rpm

54 2200 rpm

55 2500 rpm

60 3600 rpm

65 3800 rpm

72 4000 rpm

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Answer 2

Aug 17, 2011 11:49 PM in response to BaedaBln

I can add 89C - 5,500 rpm!! Now the question is why would the CPU reach 89C during the evening with me just doing some email and websurfing? I can admit spotlight was indexing my Time Machine back up but this was weeks after I made the upgrade to Lion. The fans were just roaring which is where I think Apple got the idea of this release name... 4 or 5 month old MBP with i7 and 8 GB.

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Answer 3

BaedaBln Author

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Aug 17, 2011 11:58 PM in response to CordovaBay

So far I could always correlate the temperature with some user interaction. But the question still is:

1.) is it necessary to get so much hotter with so little interaction ?

2.) is the fan speed profile changed in Lion compared to SL (I assume that the battery drain is mostly due to the fans)

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Answer 4

Aug 18, 2011 12:00 AM in response to CordovaBay

I spoke to a friend who is on the Tier 2 of the Mac support group in Apple. He said there is a problem with rogue apps in OS Lion that causes the CPU to be used often. He was not able to explain the basis but I hope to get in touch with him again regarding this.

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Answer 5

Aug 18, 2011 5:05 AM in response to BaedaBln

In job my Mac never goes above minimum fan speed (2000 RPM for both fans) yet I'm having shorter battery life than before.

But if Lion finally kicks fans to higher RPM due to temperature, thanks gods. In my old Macbook Pro running Leopard or even Snow Leopard, my CPU was getting over 100 C before fans decided to go on max (my record was 116 C while running CPU on 100% :-)) and cool it. ;-) I had a 3rd party application installed bit later where I set 80 C CPU temp for 6000 RPM...

So the problem might be more ralated to more CPU usage? (higher temps, more cooling)

Or it might be not related at all.

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Answer 6

FastTJR

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Aug 18, 2011 6:27 AM in response to jesslorenzo

@jesslorenzo

FIrst, you may want to also post this comment on the battery life thread:

https://discussions.apple.com/thread/3194235?answerId=15961122022#15961122022

Second, you may want to ask your contact why these 'rogue apps' in Lion do not show any CPU usage in System Monitor.

Fortunately, after experiencing battery life issues after first upgrading to Lion, the situation has improved very noticeably for me, but when I was experiencing them (3 hours or less), there was nothing calling off more than 2-3% of CPU usage, and that was only momentary.

I am not suggesting any of these were the solution to my battery woes, but I all I did was:

SMC reset
Calibrated battery - twice
Installed 10.7.1

I am not even aware of doing any other software/app updates (other than the Lion update).

Now I can get 5+ hours with 'normal' usage.

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