Early 2011 model, A1278 / 2.3 GHz i5 or 2.7 GHz i7 processor.

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i7 thermal throttling? Operating below its base frequency at load

Hi there.

As I've dismantled my MacBook and had to clean the logic board (in search of false contacts but this issue is solved), I had to replace the CPU thermal paste. To be sure I have applied it correctly, I ran a quick Prime95. The MacBook performs and heats up as it used too before, the pulls a lot of hot air out of the heatsink so I'm reassured.

But, as I'm curious, I've went a few steps further in the test and monitored the temperatures with HWMonitor and the CPU frequency with Intel Power Gadget.

Big surprises:

First, under full load (4 worker threads in Prime95), cores temperatures quickly climb over 95ºC! HWMonitor shows temperatures alarms triggering for "PECI SA" and "PECI GPU" that are above 90ºC. The fan speed increases to the maximum and core temperatures stabilise at around 95ºC.

But that's where the Intel Power Gadget comes in: For the temperatures to stabilise, it appears that the CPU has to throttle down to 2.0-2.1GHz!

This is worrying because the i7 should run at 2.7GHz and even higher in Turbo mode.

I haven't managed to see it reach its 3.4GHz turbo speed in single thread either...

This is the first time I've benchmarked and monitored this machine, so I'm wondering whether this is the expected behaviour for this MacBook Pro as it has a so-so cooling system???

Or if I have to reapply the thermal paste (although I'm pretty confident in my pasting with the dozens of processors and others components I've "thermally pasted" without any issue so far)... The paste I used is Prolimatech PK-1 I had in a drawer, which used to give me better results than the prior one I used to use: the famous Arctic Silver 5. I still have some.

Thanks for help figuring this out. I'll update the topic with some screenshots.

Alex.

Update (screenshots):

The reason I opened this topic:

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But after having reapplied a thiner layer (and Arctic Silver 5 this time):

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Behaviour confirmed in this interesting review of the i7 2011 MBP13: http://www.notebookcheck.net/Review-Appl...

Answered! View the answer I have this problem too

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Did you inspect the heat sink? I would get a new one and then you should weigh them on a good scale. I'll bet yours is light as the cooling fluid has leaked out.

Did you do a good job cleaning off the old paste? If the paste has been in your drawer awhile you may want to get a newer paste.

Here's some good references:

Thermal Paste Comparison, Part One: Applying Grease And More

Thermal Paste Comparison, Part Two: 39 Products Get Tested

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Well, no sign of damage or leak from the heatpipe, but could be a have been a lead.

Thanks for the links. As I said, I'm experienced at this and I trust my work. Anyway, I'll redo the job with less paste, maybe I've been too generous. I wasn't sure about the pressure this cooler apply and since the CPU was drown in a huge quantity of thermal paste from factory...

I would be glad to see users with the same machine posting results of the same test, too!

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Just replaced the Prolimatech garbage (let's call it that way) with a very thin layer of the good old Arctic Silver 5. Back to the old days! Still some thermal throttling but MINIMAL. TurboBoost also kicks in now but the MBP cooling doesn't allow it more than a few seconds. Now, cores stabilise at 2.6-2,7GHz at full torture load with rather high temperatures of 98-99ºC.

That's huge but I assume it's the way it's supposed to be with such a tiny heatsink and a powerful i7.

Confirmed in this interesting review of the i 2011 MBP13: http://www.notebookcheck.net/Review-Appl...

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Alex will be eternally grateful.
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