Fans with connected external monitor

[lancastor]

I currently own a Macbook Pro 15.4“ i7 2.2 Ghz Mid 2015. I can work with a external monitor (24“ via HDMI). The fans of the Macbook are completly silent.

Now I want to switch to a Macbook 2020 i5 10th Gen or a Macbook 16“ 5300M and connect a external 4K monitor via USB-C.

Is this correct that both Macbooks are getting very hot and the fans are spinning up when I connect a external monitor?

So that would be a huge step backwards and it would be better to keep my five years old Macbook which keeps cool and silent when I connect a external display.

 

[maflynn]

Is this correct that both Macbooks are getting very hot and the fans are spinning up when I connect a external monitor?

Its for the 16" MBP at the very least. I suspect it may not be a problem for the 13" MBP, simply because that model does not have a discrete GPU. I believe the heat is the result of the MBP's dGPU that is working harder to drive the external monitor.

 

[Raikal]

I have both devices with me right now. The 16" is causing constant fan noise (2500rpm if I'm doing absolutely nothing, some browsing and Xcode open quickly leads to >3000rpm) while the 13" is silently handling the same workload

Edit: This is when the devices are open. Clamshell mode keeps the 16" quiet (at least for me)

 

[lancastor]

Thanks for your help. 👍🏼👍🏼

So I get the 13“ model. A silent Macbook is the most priority for me.

 

[bernuli]

Now I want to switch to a Macbook 2020 i5 10th Gen or a Macbook 16“ 5300M and connect a external 4K monitor via USB-C.

My recommendation is get the new monitor first and hook it up to the 2015 and see what happens fan wise. That way you have a fair comparison when you get the new MacBook

 

[cynics]

I currently own a Macbook Pro 15.4“ i7 2.2 Ghz Mid 2015. I can work with a external monitor (24“ via HDMI). The fans of the Macbook are completly silent.

Now I want to switch to a Macbook 2020 i5 10th Gen or a Macbook 16“ 5300M and connect a external 4K monitor via USB-C.

Is this correct that both Macbooks are getting very hot and the fans are spinning up when I connect a external monitor?

So that would be a huge step backwards and it would be better to keep my five years old Macbook which keeps cool and silent when I connect a external display.

You grazed over the workload as if it wasn't the most important variable. The load on the GPU/CPU will effect the temps and thus the noise the fans produce.

Depending on specifics between those two monitors you are comparing a vastly more complex workload with the 4k monitor that the 2015 MBP can't even take full advantages of due to hardware limitations. Being quieter because your performance is lower isn't better.

Being realistic with expectations is the goal. Buy a monitor you'll use and use settings you need. Don't just max it out because you can. For example...

I use my 13" MBP plugged into a 1080p60hz monitor via a USB-C Hub with DP at work everyday. Fan rarely comes on, <50c is maintained naturally. That is of course using the MBP it for word documents, email, web browsing etc...non GPU taxing workload. If I connect it too a 4k 10bit monitor via USB-C to HDMI cable (DP Alt Mode) and play a 4k60hz 10bit HEVC video the temp bounces off 100c as the fans ramps to max RPM to try to move the heat out of it.

 

[FilmIndustryGuy]

I just got the 16" base connected it to the 21.5" 4K LG UltraFine monitor via USB-C. someone on here told me ho fan issues on their end with this setup but this is what I see on my end. Seems the Video card is maxing out. Is this within normal? I'm watching Netflix on 16" and a document on the 21"

 

[lancastor]

What is the name of this OS X tool to show the detailed temperatures?

 

[MrGimper]

What is the name of this OS X tool to show the detailed temperatures?

https://bjango.com/mac/istatmenus/

 

[Patcell]

I just got the 16" base connected it to the 21.5" 4K LG UltraFine monitor via USB-C. someone on here told me ho fan issues on their end with this setup but this is what I see on my end. Seems the Video card is maxing out. Is this within normal? I'm watching Netflix on 16" and a document on the 21"

It looks like just the VRAM (frame buffer) on the GPU is maxed out - the video card isn’t actually processing much. Your fans are spinning pretty fast there, but your CPU temps are quite low.

I do not have a 16” machine, but based on what I’ve read, Apple made the choice with the 16” to be more aggressive with the fan curves to keep thermals in check. While in the past 15” models they favored higher CPU temps and silent operation. What you have mentioned above I do quite often on my 2017 15” Pro and I do not hear the fans, but my CPU temps are about 10C higher.

 

[YabsterDE]

This seems to be a common behavior with the 16" and external monitors. Due to the thunderbolt architecture, an external monitor ALWAYS triggers the dedicated GPU, which adds more wattage and heat to the system (8-20 watts more depending on open or closed lid); while the CPU is mostly around 3-10% the fans spin up to keep the temp. down.

Apple Support Forum and several theads on all mojor apple related sites users confirm this behavior AND it's annoying

e.g. https://discussions.apple.com/thread/250878229?page=164 (yes, it's already 164 pages long
or

(2019) 16" is HOT & NOISY with an external monitor! :(

Damm yeah I reckon this is it you know 🤯. If you scroll further down interestingly the article even explains that if you match your monitor to "correct timings" you'll avoid the issue. It could certainly explain why certain monitor configurations have been reported to work fine. It could even...

forums.macrumors.com

if your prefer the only-65-pages local thread 😋

People returning their units, some say it helped getting a new machine, others got the same problem with their 2nd and 3rd replacement devices...sent mine in aswell, no HW issues found, currently checking with Apple Support the 3rd time.

IMHO: To me it seems to be a combo of soft- and hardware issues. Thunderbolt/USB-C/GPU connection, METAL API (defaulting to eGPU and external display refresh rate for all apps which uses METAL) = too much base heat in the system with i9/dGPU/TB3-port etc.

 

[lancastor]

Due to the thunderbolt architecture, an external monitor ALWAYS triggers the dedicated GPU, which adds more wattage and heat to the system (8-20 watts more depending on open or closed lid)

Which case keeps the Macbook cooler?

1. Close lid (clamshell mode) because the GPU don’t have to drive two displays (extarnal and internal)

or

2. Open lid, because the cooling/ventilation gets better?

 

[YabsterDE]

Most people say 1. and that's what i observed, too. Better ventilation is negligible.
20+ watts fot both displays put out too much heat with a system operation close to the edge at idle, already.
The real problem is that on top this each apps that uses METAL (for GUI draw etc.) seems to add up to the wattage aswell, e.g. Logic Pro X or Final Cut. So closed lid, around 8 watts, Playback Logic, around 18-24 watt. As i said IMHO a combo of HW and SW issues.