cpu underclocked all the time!

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ThomasD3 Author

Level 1

46 points

cpu underclocked all the time!

I have a MBP 2011 with Sierra.

Suddenly, yesterday, it started to become very slow.

I was using logic pro and suddenly I had that warning that the system can't handle the load in real time.

Since then, the computer is overall very slow.

It will not even play a single track in logic pro without a timeout, but everything else has slowed down:

Firefox will take 4-5 seconds to load (off a SSD), opening mail is super slow too, etc.

So, here what is interesting:

this computer was always running hot (like 70c / 160f) at idle, going in the high 90c / 200f on load.

now it is running at 45c / 113f on load...

There is no abnormal CPU usage and even if I run CPU intensive applications, it will show a high cpu usage but not heat up, yet run very slow.

It is exactly as if the CPU was running on a low clock at all times.

So, I ran intel's tool and that's exactly what I found: the CPU is running at 0.8GHz!

No amount of reboot, clearing the NVram, etc changes anything; I tried 2 chargers also to make sure it wasn't a power supply problem.

What could be causing this?

MacBook Pro (15-inch Early 2011), macOS Sierra (10.12)

Posted on Oct 13, 2016 6:13 AM

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Answer 1

JimmyCMPIT

Level 7

29,306 points

Oct 13, 2016 6:19 AM in response to ThomasD3

you may post an etrecheck report for further analyis

www.etrecheck.com

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Answer 2

ThomasD3 Author

Level 1

46 points

Oct 13, 2016 8:06 AM in response to JimmyCMPIT

I have looked at the output of etrecheck, nothing is out of the ordinary; I tend to manually prune kext leftovers, etc so the system is quite clean.

however, we found something very interesting: it is linked to the power supply.

2 power supplies exhibit that problem, 1 doesn't..

The computer work normally with one of the power supplies and goes back to normal speed, etc; the other two have the computer run at low speed.

The other mac works properly with all the power supplies.

I'm going to install istats to see the voltage values since now I know where to investigate; the problem happened suddenly while using logic pro, during the middle of the session, so it's not software related.

I'll check what the voltage sensors say and how much power is drawn.

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Answer 3

John Galt

Level 10

155,810 points

Oct 13, 2016 8:49 AM in response to ThomasD3

Are they all identical power supplies? Identical model numbers with identical ratings? If they are, take all of them to an Apple Store for evaluation, along with your MBP.

Please read Apple Portables: Troubleshooting MagSafe adapters - Apple Support.

Apple power adapters contain a device that communicates with the MBP using a one-wire serial communication protocol. No one other than Apple knows the extent of those communications, but it can be assumed they are bidirectional and not trivial.

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Answer 4

ThomasD3 Author

Level 1

46 points

Oct 13, 2016 10:03 AM in response to John Galt

One is from a MBP 2010, another from the MBP 2011, the third one is from 'some mac at the office', so really no idea.

But yes, having the store identify them could be a good idea, thanks! I'll talk to them tomorrow.

In the mean time, with iStats menu, the voltages are exactly the same but they're very similar. I would have expected vcore to be very stable, but it's varies a little bit (identical load all along, or as identical as I can make it really).

I don't know if slight variations are normal on the MBP motherboard: it could be a capacitor gone bad and not filtering the fluctuations; this would still keep the board in working order, so it is a definite possibility.

does anyone know what's the acceptable swing for vCore on a MBP motherboard? (for a specific load)

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