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Q: 2015 MacBook Pro 15" severe CPU throttling

My 15 inch 2015 MBP (2.5ghz i7, m370x, 512gb, OSX 10.11.4) is suffering severe CPU throttling while the discrete GPU is active.

Test 1: FCP X render from cold boot:

https://youtu.be/ZVUx2vFxSXw

Test 2: FCP X render + Handbrake 4K → 1440p video encode from cold boot:

https://youtu.be/m_dckNFrKk8

My laptop is suffering severe throttling, with typical CPU clocks in the 1-1.5ghz range. Curiously, though, CPU wattage and temperature are very low (15-20w and 70-75C respectively). The computer is in a well-ventilated area as well and fan speeds are at max (~6000rpm).

(For a point of comparison, here’s test 2 running on my 2015 27inch Retina iMac, with no throttling whatsoever:https://youtu.be/gQMabqB_-xA)

The laptop’s CPU doesn’t throttle when the discrete GPU is completely inactive (when the laptop is on integrated graphics). When the discrete GPU is active but idle, I still see some amount of throttling (CPU clocks in the 1.7-2.2ghz range):

https://youtu.be/Q5XXAPxmz3c

I brought my laptop into a local Apple Store, and they ran a series of diagnostics on the laptop. They told me that the laptop passed all of their internal diagnostics and that I should treat the throttling as “expected behaviour” for the laptop.

I’ve never seen this kind of throttling with any Apple computer I’ve ever owned. What should I do from here?

MacBook Pro with Retina display, OS X El Capitan (10.11.4)

Posted on Jul 21, 2016 8:52 PM

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