Reprogram SMC to run off of different sensor

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Level 1

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Reprogram SMC to run off of different sensor

Hi friends,

So recently I have come across the dreaded SMC sensor error which throttles the CPU, ramps up the fan to max and has a stuck recorded temperature input of 128°C. I have discovered that by reinstalling El Capitan and try all other methods of fix that this is a hardware issue. ALTHOUGH, I tried out some 3rd party software to check my temperatures of each core and receive all other sensor temperatures in the machine. There was no temperature reading which said 128°C or anything remotely close to it. This leads me to believe that there is another possible fix to the problem.

After taking the machine to apple they said that the only way to fix the issue was to replace the logic board which would cost approximately $800. But I will not give up because I have a solution that just might work with the help of some savvy developers and programmers.

What I'm reaching out for is a way to reprogram the SMC to use the average temperature of all recorded CPU temperatures (all cores, CPU proximity, CPU PECI) and using that to drive the fan controller.

Why do I want to do this? A lot of people have had this problem and people with more recent macs, which most methods don't work for, that have this problem have no option other than taking it to apple and pay around $800 for a logic board replacement. Usually I would pay for the replacement but I just can't afford it at the moment and I have use my laptop for school.

I am using a Macbook Pro 13" Retina 2.6 GHz with 16 Gb of RAM and a 256 Gb SSD from early 2013. It is currently running the latest version of El Capitan (10.11.2) with all updates available installed

MacBook Pro with Retina display, OS X El Capitan (10.11.2), 2.6 GHZ. 16 Gb RAM. Early 2013.

Posted on Dec 24, 2015 10:38 PM

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Answer 1

OGELTHORPE

Level 9

57,329 points

Dec 25, 2015 4:59 AM in response to Limo1300

If the MBP temperature was 128*c, it should have initiated the thermal shutdown circuits well before reaching that level. Either the temperature monitoring program is faulty or your MBP has a serious hardware problem.

Your premise that 'averaging' the temperatures will be a solution is a faulty one. Only one item has to exceed its operating limits to bring the entire system to a halt. Averages are meaningless in this situation.

Ciao.

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Answer 2

Limo1300 Author

Level 1

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Dec 25, 2015 9:00 AM in response to OGELTHORPE

The MBP temperature isn't actually 128ºC. That's just the reading the system automatically gives when there is no input from the SMC temperature sensor, which is broken. The third-party software I am using is called TG Pro and has given me the accurate temperatures of everything NOT by using the SMC sensor, but by using each individual components' integrated sensor.

So basically what the SMC in the Macbook is doing is since it isn't receiving an input from its thermal sensor, it is taking the highest safety precautions possible. This means ramping the fans to full RPM and throttling the CPU to prevent a large heat output. It's like a backup preservation system.

What I want to do is have the SMC utilize each of the CPU sensors available and finding the median of aforementioned sensors and sending that temperature to the SMC.

For example, (using the picture above) we find the median of the CPU sensor temperatures [38 + 41 + 40 + 43] / 4 = 40.5. We then round to the nearest degree which is 41ºC. 41ºC is then sent to the SMC and the SMC uses the fans to react accordingly.

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Answer 3

OGELTHORPE

Level 9

57,329 points

Dec 25, 2015 10:08 AM in response to Limo1300

If I have one hand in a freezer and the other in a fire, the average may suggest that I am comfortable, but that would be far from reality. I simply cannot agree with your premise that such an average will produce any meaningful data. It is important to know how each individual component is functioning and responding so that if there is a problem, one knows exactly which component is malfunctioning so that that appropriate corrective action may be taken.

Ciao.

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Answer 4

Limo1300 Author

Level 1

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Dec 25, 2015 11:10 AM in response to OGELTHORPE

Very good point. Okay then. Instead of using the median temperature, we'll use the highest reported temperature coming from any of the sensors which were listed in the picture from my previous post. How does that sound?

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Answer 5

OGELTHORPE

Level 9

57,329 points

Dec 25, 2015 12:04 PM in response to Limo1300

It does not take long to scan that output to make a determination where the highest temperature is, so in effect you have the highest temperature already identified.

I have grave doubts that Apple is going to modify the OSX per your suggestions, but if you wish to pursue this, you may post your thoughts here:

http://www.apple.com/feedback/

Ciao.

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Answer 6

Limo1300 Author

Level 1

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Dec 25, 2015 9:05 PM in response to OGELTHORPE

Thanks, I will post there too. But I created this forum post to call out to developers and programmers who may be able to help me achieve this.

I'm not calling out to Apple directly, but want the community to assist me in reprogramming the SMC as I don't know the first thing about programming, let alone a mac System Management Controller.

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