Q: Fan Speed increases with Thunderbolt Display

The TB display puts a load on the GPU system, Graphics card system, and makes the whole system heat up. Normal from what I see.

Actually, I have the same problem when connecting a screen with the thunderbolt to DVI adaptor. What I have found out, is that the fans kick in only if I connect the Ethernet plug. When I run the same screen with WiFi, no Ethernet, all is fine. My guess is that it is the Ethernet connection, rather than the screen.

My setup: MacBook Pro 17 late 2011, 16Gb RAM OSX 10.8.2.

I have the same computer (Late 2011 MBP 15") and have noticed the same thing when plugging into a thunderbolt monitor.

Did a bit of research on this and as you probably know, the MBP has two video cards, an Intel HD Graphics 3000 and a more powerful AMD Radeon HD 6750M (or other Radeon). Usually the AMD Radeon doesn't power up unless you're using a demanding graphics application like a 3D game. However it also powers up to drive any external monitor, and there doesn't seem to be a setting to turn this off.

So it doesn't seem like there's any way around generating a lot more heat whenever you have an external display connected and thus the fans will need to work a little harder to keep things cool. Just for reference, I'm not doing anything demanding on my computer right now but am connected to a TB display and I can hear the fan noise a little bit but it's not bad, and using smcFanControl my fans report to be spinnning at about 3600 RPM.

I wish there was a way to drive the external display with the Intel Graphics as I almost never hear the fans when not connected to a TB display. If anyone has any better info, please let us know!

I have a Late 2011 i7 2.5ghz 15" MBP, with one Thunderbolt display, my fans are around 2200 with nothing on. The moment I open Safari or Chrome, fans kick up to about 4k. I just bought another Thunderbolt display, daisy chained it and observed my fans kicked up to 6.2k regardless. The fans are ridiculously loud. I'm guessing this is normal, but annoying. I think I'm going to have a dedicated table fan blowing at my Macbook. The GPU is at 58º, and CPU is at 70º, and both have been on for about 2 minutes.

If you're not using your MBPr screen turn it off and keep the lid open for the air flow. That should help keep temps down as the GPU won't have to power 2 screens.

Hey everyone, kkwan77's idea worked for me.

I plugged into the thunderbolt and then closed my MBP's lid almost all the way, until the screen on the laptop went dark and my dock automatically transferred to the thunderbolt's screen.

Before with both screens active my computer's temp was running over 80 degrees C which made the fans spin at 3600+ RPM very noisily as I posted before. With only the thunderbolt screen, I'm holding steady between 63 and 65 degrees C, and my fans are completely inaudible, at the speed of 2000 RPM which is the same speed they were at when not plugged into the thunderbolt.

Thanks kkwan77, you're brilliant!

-liquidki

If it works for you, give my post a like. 

Also to take it a step further you can turn off the MBPr screen completely with the lid fully open for increased air flow.

On mobile atm, so take a look at my posts on how to do this. If not I'll reply later with steps.

Here's the steps to turn off the MBPr screen with the lid fully open.

Remember as the instruction states once you enter in the commands in terminal you have to close the lid on bootup and restart and waking up from sleep mode. Once the logo screen appears you can reopen the lid and the screen will be off. (e.g., bootup: immediately close the lid, login screen appears, then you can open the lid)

Now you internal temps should be much much lower and the fan shouldn't kick up.

To execute in Terminal:

sudo nvram boot-args="iog=0x0"

To undo in Terminal:

sudo nvram -d boot-args

Once you type it into terminal I believe you need to enter your password. I then restart my machine. Now the TRICK is to either restart your machine with the lid already closed (hit restart then slam the lid!) OR turn the machine on for the first time (then quickly slam the lid!) once you are past the login screen you can open the lid.

ALSO: if the machine is asleep, and you simply forget and open the lid, it will wake up both displays. So just remember to wake the machine up with an external bluetooth mouse or keyboard.

I face this issue with my newly purchased MBP 15" (Mid-2015). I am considering to return it and buy another one with integrated graphics.

Does anyone know if the model with integrated graphics (Iris Pro 5200) overheats too when it drives both the internal and external thunderbolt display?

I appreciate also any information on what I lose by the downgrade to the integrated graphics from the screen resolution and quality of picture on the Thunderbolt display for normal everyday use applications.

Thanks.

I would also be very, very curious about downgrading to integrated graphics. Any news on fan noise as well as downsides?