rMBP Late2013 Faster in Clamshell mode

[finnschi]

I think I stumbled upon something here,

I wanted to check how much my CPU was Throttling under heavy load and I saw my CPU going down to 2.8 /2.9 Ghz while in Clamshell mode albeit at 99C

Now, I wanted to test if opening the laptop would yield any different result due to improved thermals but what I found out that while powering both laptop screen and an external Display my CPU would throttle down to 2.4 /2.5 Ghz, temperature dropped to around 89C.

Then I did another test and ran the rMBP with the Lid open and no display connected, and the results where the same as in clamshell mode, same temperatures, same clockspeeds, so opening/closing the lid does not seem to have a big impact on thermals.



Anyone with an educated guess why that might be?


rMBP Late 2013 , 16Gb Ram, GT 750m, 2.3Ghz i7 on 10.11.5

Clock speed Readout with Intel Power Gadget, stress tested using the "yes" command in terminal for 12 Stress test threads.

 

[RoboWarriorSr]

How high of a resolution is the external display? Sounds like the cpu is throttling allowing the GPU to work faster, after all the 15" is running a 3K+ display and connecting an external display only works the GPU harder. The computer is already running 5,184,000 pixels with the internal display, adding a 1080p display adds another 2,073,600 pixels.

 

[Samuelsan2001]

The thermals are for the overall machine, so if the computer is in clamshell it is using less heat to run the external screen using ten GPU and therefore has more thermal overhead for the CPU to run a bit faster.

 

[finnschi]

The External Display is a 3840x2160 Resolution Screen, I have forced the gt 750m to be always on.

I might try to just drive a 1080p screen to see if that changes anything, it seems to be a software thing though because the throttle hits right at the moment I connect the display, and really just showing my desktop on a external screen should not use those kinds of power, I mean a 4-500Mhz Drop for just running a screen, while my GPU is not really doing anything? Think about it, a iPad could drive a resolútion like that..

 

[RoboWarriorSr]

The External Display is a 3840x2160 Resolution Screen, I have forced the gt 750m to be always on.

I might try to just drive a 1080p screen to see if that changes anything, it seems to be a software thing though because the throttle hits right at the moment I connect the display, and really just showing my desktop on a external screen should not use those kinds of power, I mean a 4-500Mhz Drop for just running a screen, while my GPU is not really doing anything? Think about it, a iPad could drive a resolútion like that..

Yes then that does seem normal, the iPad cannot run another external display only the internal one. At this point your mac is running a total of 13,478,400 pixels all presumably at 60 hz while an iPad only needs to run 3,145,728 pixels (iPad Pro 9.7") or 5,596,136 (12.9"). In addition, UX on the mac is considerably more graphic intensive considering the numerous applications that need to be drawn simultaneously while also have to deal with blur. So comparing to an iPad is not a fair comparison, in which an iPad cannot run 13,000,000+ pixels very well.

 

[Creep89]

This is why I really want to have a new MacBook Pro with a proper dedicated graphic card. I ran into the same problem with my rMBP Late 2013, but with a i7-4960HQ. But I fear Apple is not interested anymore in selling pro laptops, but rather consumer laptops with a fake pro on it.

 

[jerryk]

Sounds like it ran hotter with both the laptop display and external working, and throttled harder which dropped the temps lower. Seems like PID type control which is similar to a shock absorber.