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MacBook Pro 2018 CPU throttling? There’s another theory out in the wild

The launch of the most powerful MacBook Pro notebooks ever have been overshadowed by reports the most powerful of all is quite not as powerful as it should be.

In early tests the i9 processor-equipped 15-inch MacBook Pro displayed signs of CPU throttling under heavy loads. Instead of the advertised speeds of 2.9GHz, one user said he was achieving speeds closer to 2.2GHz. This is naturally an issue for someone who paid £2,700 for a laptop computer.

The suggestion has been that the throttling is happening to guard against overheating. Users who’ve placed the laptop in the freezer while running power hungry processes like video editing have seen speeds closer to the advertised. Apple is yet to comment on the story.

However, a new theory posted to Reddit suggests something else may be in play beyond thermal throttling of the CPU. Poster randompersonx says (via 9to5Mac) the issue is being caused by power throttling of the voltage regulator module (VRM).

The poster claims he was able to fix this by overwriting power settings within the Mac. If this proved to be the issue, it’s something that could potentially be resolved by Apple in an update.

In the post, the Redditor writes:

“The ultimate root cause of the very bad performance drop during the throttling is not thermal throttling of the CPU, but rather power throttling of the VRM (voltage regulator module), being unable to satisfy the power desires of the i9 CPU.

“When the VRM maxes out (overheats … but this is different from CPU thermal throttling), the motherboard sends a signal to the CPU to drop its speed to minimum (800Mhz) to allow the VRM a chance to cool down. The CPU then returns to it’s previous desire to pull maximum power, spins up to high turbo speeds, and the cycle repeats again. When the CPU keeps switching from Turbo to 800Mhz, it is in a very inefficient state, so the amount of work being done relative to the amount of power drawn decreases.”

The poster has provided instructions to change the settings, but we certainly wouldn’t advise that you follow them at this stage. The best course of action is to grin and bear it right now and see if Apple makes a statement (and now it has). Either that or return the machine to Apple.

Have you experienced speed throttling issues with your new MacBook Pro? Share your stories with us @TrustedReviews on Twitter.

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