![]() By preventing the VRM from maxing out, the OP was able to achieve sustained turbo speeds with about 20% higher performance. Anecdotal evidence in the same thread points to the fact that this how Apple has been manually setting the VRM limits on its own all this while but this is the first time that it has used a chip capable of drawing much more power. ![]() Thus, the MacBook Pro struggles even to attain the base CPU clock. The constant cycling between the turbo speed and 800 MHz proves every inefficient and can also prove detrimental to the VRM itself in the long run. Since the VRM is not able to supply the required steady power limit due to overheating, the motherboard signals the CPU to slow down to 800 MHz to allow the VRMs to recuperate. Testing by the OP has revealed that the VRM can supply up to 49W before maxing out (not counting the GPU). The problem here is that these are Intel recommended settings for this processor, which assumes that you are able to supply 100W for the steady state. Doing the math, the OP says that Apple has shipped the Core i9 MacBook Pro with CPU regulation power (Power_Limit_2) set at 125W for 28 seconds and Steady State limit (Power_Limit_1) set at 100W. This also involves forcing the MacBook Pro to load unsigned kexts so you should tread at your own risk before proceeding. This involves some command line work and understanding HEX codes but a technically comfortable person should be able to follow the given instructions. The OP goes into detail about the issue and offers a temporary mitigation to the problem. Turns out, it is the inability of the Voltage Regulation Modules (VRMs) to supply the required power to the CPU due to overheating that is causing it to throttle. While the decision to put a Core i9 CPU in such a thin chassis is a matter for another discussion, a Reddit user by the name randompersonx has detailed his findings as to why such high throttling is seen. Recently, popular YouTuber Dave2D had to put his Core i9 MacBook Pro in the freezer to offset some of the throttling effects. The 2018 Apple MacBook Pros with Core i9 CPUs have been in the news for poor thermal management leading to throttling under load.
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