If your 2018 MacBook Pro laptop is slowing down unexpectedly, then download and install today's macOS 10.13.6 Supplemental Update, and cross your fingers.
This patch attempts to address frustrating slowdowns experienced by owners of Apple's latest top-end 13in and 15in notebooks that use eighth-generation quad and six-core Intel Core i5, i7 and i9 processors. The update frees the latest 15in MacBook Pros to run up to 70 per cent faster, and 13in Touchbar MacBook Pros up to 100 per cent faster, we're told.
That's quite a jump.
The performance hit appears to be the result of the system substantially throttling the processor while handling heavy workloads, such as video editing. The hardware slows down the CPU cores below their base frequency, to the point where even a super-duper 2018 Core i9 MacBook Pro runs slower than a 2017 Core i7 MBP.
Here's a video by technology vlogger Dave Lee demonstrating the effect:
If you just splashed out four figures for this year's MacBook Pro, you're probably fed up with the performance crash, so try out today's patch. The software is only available for affected Macs.
According to one savvy sleuth in the MacRumors forums, it is possible Apple set the hardware registers of its chipset in a way that causes a voltage regulator on the motherboard to severely throttle the processor if it draws too much power.
For example, it's claimed the Core i9 in the Macbook Pro is programmed by Apple to draw up to 125W in turbo mode for bursts of up to 28 seconds, and gobble up to 100W normally. This level of power draw is Intel's default for desktop PCs but too much for the portable laptop's voltage regulator module, which triggers a signal to the processor to hit the brakes, we're told. This clock slowdown forcibly kicks in when the power draw goes north of 50W, it is claimed.
Thus when you give the CPU cores a lot of work to suddenly do, they hit the gas, ratchet up their clock frequency to get the job done, and consume so much energy they make the motherboard hardware force them to slow down, it is claimed.
The fix, it appears, involves managing the system's power usage a great deal better – and at a higher level by taking into account CPU and GPU load, rather than throttling at the voltage regulator module level.
In a statement to tech journalists, Apple said a "missing digital key" in its firmware is to blame. This perhaps means a driver that properly manages the thermal output of the chipset was unable to load, as a result of this missing key, causing excessive hardware throttling to fire up in its place. Apple's spokespeople stated:
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. Customers can expect the new 15-inch MacBook Pro to be up to 70% faster, and the 13-inch MacBook Pro with Touch Bar to be up to 2X faster, as shown in the performance results on our website.
Apple did not respond to a request for more information. Be aware that your shiny laptop, with this update in place, will still throttle itself when busy with lots of work, to prevent itself overheating. It should just not strangle itself quite as dramatically. ®