Throttling in New i9 MacBook Pros Appears to be Due to Power Delivery Chip

MacRumors

macrumors bot
Original poster
Apr 12, 2001
7,446
8,512



A user posting on reddit and in the MacRumors forums has given a detailed account of their findings and attempts to circumvent the throttling previously discovered on the new MacBook Pro 15" models featuring the six-core i9 Intel CPUs.

The user goes on to explain that one of the internal power limits set for the device may not be appropriate for the power draw of the CPU and identical to previous MacBook Pro models, causing the power delivery chip (known as a voltage regulation module, or VRM) to report an over power condition that forces the clock of the CPU down to scale back power. This sets up the same conditions to allow throttling to occur once again.

These conditions may be presenting themselves due to the new six-core design of the i9 CPU featured here. While Intel increased the core count of the CPU, they did not increase the thermal design power (TDP), or the amount of dissipated power manufacturers should plan to have to cool for a proper CPU design. This is an issue because this number usually reflects normal usage, and does not account for turbo modes. It's also likely it can exceed the draw of previous four core CPUs given the similarity of clock speeds and process nodes they are featured on.

A method for tuning this limit is provided in the post, but it requires executing a command manually or via script each time the computer boots, and would likely void the warranty if Apple technicians discovered it. Still, the user posts results of benchmarks showing successive runs with no throttling. Manufacturers will always quote likely reduced component lifetimes if used outside of their specifications, but the results appear stable, and there is no thermal throttling of the CPU, the original suspected cause of this issue.

This fix will not address total system power draw becoming excessive, such as long sustained loads from the CPU and GPU, but it is possible Apple could issue a fix similar to the one outlined in the reddit post that is stable.

As for whether this issue is related to the hardware design of the MacBook Pro, that is possible as well. While iFixit's complete teardown of the current 15-inch MacBook Pro is not yet available, the previous teardown reveals significant differences in the VRM chips that power the GPU and CPU of the device.

GPU power components

The GPU power components seen above are on the top side of the logic board near the GPU die, and thermal grease can be seen on the components, indicating that they interface with the heatsink in the device. This is in contrast to the same components for the CPU, which are featured on the rear side of the logic board with no thermal interface to the top of the package, as seen below.

CPU power components

Additionally, the publicly available data sheets for these parts indicate more differences that suggest their thermal profiles will be different. The International Rectifier part for the GPU features a lower thermal resistance, meaning it can better dissipate its heat to the surrounding areas (board, air, heatsink) than the Intersil part for the CPU. Additionally, it boasts a higher power efficiency, meaning it dissipates less power itself to deliver the same amount of power as the Intersil part.

Along with the heatsink path provided for the IR parts, it's clear they will not be capable of driving the same amount of load in any sustained mode. This makes sense given GPUs can see high loads for longer periods, but this could be an area of improvement for future MacBook Pro models from Apple, especially since it has typically chosen GPUs with very similar thermal design power limits (TDPs) to the CPUs in its MacBook Pro line.

Article Link: Throttling in New i9 MacBook Pros Appears to be Due to Power Delivery Chip
 

Winter Charm

macrumors 6502a
Jul 31, 2008
803
268

jsalda

macrumors regular
Jun 6, 2008
168
282
This is very sad, Apple is so focused on iPhones, they have forgotten the power users who actually make content and Apps for iPhones, Macs and iPads.
I feel this is more Intel's fault. Apple is caught in the middle, power users want the latest and greatest chips and Apple is trying to fulfill that request, but Intel's ability to deliver is lacking. This isn't just an Apple issue, any other manufacturer that uses these chips is going to have the same issues.
 

johnalan

macrumors 6502
Jul 15, 2009
333
279
Dublin, Ireland
I believe that's the same user. The reddit post got much more notice, due to the larger audience, but yeah.

Also, this is much worse than a Fan/Thermal paste issue. This will require a motherboard redesign to fix. :/

Not really, the volatile clock ramping can be addressed by changing the power draw from the VRM.
 

aka777

macrumors 6502a
Mar 13, 2012
816
370
I feel this is more Intel's fault. Apple is caught in the middle, power users want the latest and greatest chips and Apple is trying to fulfill that request, but Intel's ability to deliver is lacking. This isn't just an Apple issue, any other manufacturer that uses these chips is going to have the same issues.
Considering that apple basically adds an extra 0 to $ amount of everything, they should have figured this out.
 

hawkeye_a

macrumors 65816
Jun 27, 2016
1,260
3,232
Wouldn't sustained high power usage (gaming/video-encoding) after applying the "patch" mentioned in the article cause damage due to over-heating? Or are these components throttled based on temperature independently from the chips mentioned in the article?
 
  • Like
Reactions: Mal Blackadder

johnalan

macrumors 6502
Jul 15, 2009
333
279
Dublin, Ireland
The good news here is that this can be effectively addressed with voltage config changes.

The machines will then be much more stable and still fast.

The question is when will Apple initiate the change.
 

IPPlanMan

macrumors 6502
Dec 25, 2009
274
1,192
Apple either knew and it said “**** it, ship it.”

Or it didn’t know because it didn’t adequately performance test it.

All Apple had to do was run this test to see the issue.

Apple isn’t even trying anymore. They know we’ll buy it anyway.
 
Last edited by a moderator:

johnalan

macrumors 6502
Jul 15, 2009
333
279
Dublin, Ireland
Apple either knew and it said “**** it, ship it.”

Or it didn’t know because it didn’t adequately performance test it.

All Apple had to do was run this test to see the issue.

Apple isn’t even trying anymore. They know we’ll buy it anyway.
I know what you're saying but I doubt they would trade the hassle/embarrassment they got from this for the effort in testing.
 

Polymorphic

macrumors regular
Dec 23, 2010
112
358
Oversights like this just give more credence to rumors that the Mac team at Apple has been gutted by resignations and retirements over the last few years.

Once upon a time, people like me paid a premium for Apple products knowing that the beta testing had already been done.

Now, I have a difficult time determining which Mac I find to be the least compromised and objectionable.