In the past week, there’s been a lot of news and discussions about Apple’s new MacBook Pro laptops for 2018, including the 15-inch models which have Intel’s mobile Core i9 processors. These are adaptions of the desktop chips from the Coffee Lake family, featuring six cores, gobs of cache, and hyper-threading. However, Core i9 processors are typically found in much thicker notebooks. Apple’s design is rather thin, and this lead to some very noticeable power throttling on the notebooks even when plugged into a charger. Arguments about the issue have been all the rage over forums and websites, and Apple has now finally confirmed the issue along with a proposed fix to improve the processor’s performance.

According to a statement given to the press, the company said that the fix would be included in a 1.31GB supplemental update to MacBook Pro users and is already available through the macOS update service. Here’s the full text:

“Following extensive performance testing under numerous workloads, we’ve identified that there is a missing digital key in the firmware that impacts the thermal management system and could drive clock speeds down under heavy thermal loads on the new MacBook Pro. A bug fix is included in today’s macOS High Sierra 10.13.6 Supplemental Update and is recommended. We apologize to any customer who has experienced less than optimal performance on their new systems.”

The throttling issues began to appear when late last week Apple started selling their new MacBook Pros online and in-store in the United States. Reviewers such as Dave Lee and Marques Brownlee found performance issues right out of the box in their tests, and in various workloads the new MacBooks were slower than the previous generation. It wasn’t even a heating issue either – thermals were still in line with the previous generation, despite adding an additional two cores into the mix, along with slightly upgraded discrete graphics cards from AMD.

Reddit users on Apple-centric forums started to look into the issue and one user by the name of “randompersonx” posted up a guide to fixing the performance issues. According to randompersonx, Apple had been shipping their notebooks with a default power profile supplied by Intel for several years, going as far back as Haswell. When the rest of the PC industry made the jump to Intel’s “new” 8th Gen Core processors from the Kaby Lake family, which finally put quad-core options into the Core i5 U-series lineup, Apple held back and continued shipping their older 2017 MacBooks without any alterations. The jump to Coffee Lake was Apple’s first foray with Intel’s 8th Gen processor family, and their default power profile wasn’t adjusted to suit the new processors.

Source: Dave Lee

The fix issued by Apple mimics the guide posted to Reddit with the power fixes, and performance is reportedly finally on par with expectations. Apple’s 2018 MacBook Pro family is now around 30% faster than the 2017 models in most workloads, and only software that runs on a single core is still impacted. Apple’s power delivery isn’t capable of boosting the processor to its maximum turbo frequency, but as Dave Lee shows in a follow-up video here it’s still far better than what users had to deal with before.

Interestingly, Apple’s fix for the Core i9 throttling issues has also raised performance slightly on older MacBook Pros going back to 2015. Apple’s fix is made in the CPU governor, not in the firmware for the processor, so the blanket fix applies to several generations of Intel hardware. Tests looking at this are still anecdotal (and mostly limited to Reddit users), but it would be a neat side effect of the patch.

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