MacBook Pro Late 2018 (Vega) CPU throttling down to 1.4Ghz. Why?

[TheRiddler1982]

Hi all,

In July 2018, I have read about the CPU throttling issues on the Mid 2018. Later, Apple released a firmware updated addressing the issue. When releasing the October update with the Vega GPU, the thermal design improved.

Two month ago, I got the MacBook Pro with the Vega 20 GPU and the CPU upgrade (6 core). Now, I am doing really intensive Adobe Lightroom exporting and the CPU speed dropped to 1,4GHz although the temperature is arround 70° Celsius. Fans are rotating at 6.000rpm. All cores utlized. Screenshot from Intel Power Gadget is attached.

Exports takes forever. My Mac Mini 2014 Core i7 peforms better .

Is this a bug or a feature? Will upgrading to the latest beta address that issue?


Thanks for your assistance.


Bye,
Sven
[doublepost=1559481890][/doublepost]Export is done and CPU speed is getting back to spec

 

[SoyCapitanSoyCapitan]

Speedstep and the task you are trying to do. Lightroom is a demanding app. This happens even on desktop water cooled systems too so don't expect to work around laws of physics and Intel's chip limitations inside a laptop.

 

[TheRiddler1982]

But why is it throttling at 70° Celcius? CPUs can handle 90° without problems.

 

[Thysanoptera]

The Vega GPU must be active. Get iStatMenus and see its power usage.

 

[TheRiddler1982]

So, the numbers from the Intel software are not valid due to the usage of the Vega GPU?

 

[Thysanoptera]

So, the numbers from the Intel software are not valid due to the usage of the Vega GPU?

No, they're valid, show correct values. You have a 50W dGPU, CPU that should be able to maintain 55W but can boost to 80W, both connected with heat pipe and affecting each other temperatures. The system is designed for about 80W total power (look at your power adapter) which needs to cover also stuff like the screen, memory etc, so if the Vega is active CPU needs to be clocked down to stay within power and thermal budget, and Apple prioritizes dGPU performance.

@leman did some torture tests on his Vega machine last year, but even then his CPU clock was staying higher than what you have. So, looking at the CPU trend it is impossible to tell exactly what is going on in your case. Post numbers from some hardware monitor (like iStatMenus) that show power usage and temps of CPU, GPU and totals. Your CPU is most likely power throttling (because there is still thermal headroom). One thing that stands out is large difference between core and total package power, it is almost like the iGPU is also in high power state.

 

[TheRiddler1982]

Hi @Thysanoptera,

thanks for your detailed insights. I follow your arguments and it makes sense as you desribe the behavior. I have to get iStats and have to verify that the internal graphics unit was active, too.

Anyway, the tendency is ok so far, it's a feature