If you’ve not yet updated to OS/X Sierra you may want to wait for the 0.1 release.
Many users experience no issues when upgrading but more than a few are finding they need to do some fairly drastic things to get their system working as normal. There are numerous reports of people doing a simple SMC Reset (hold down Ctrl + Shift + Option and press power) to get things back to normal. Others are having to perform full “clean installs” of Sierra to get things back to normal.
Sierra OS/X Issues
In a brief search for OS/X Sierra problems there seems to be numerous issues related to two critical areas of the operating system: Display Management and Thunderbolt I/O.
Dual Thunderbolt External Monitors
Personally I am having an issue working its way through Apple Support related to the use of dual Thunderbolt-port connected external displays. Whenever I connect and turn on two monitors, one connected to each TB port, the FAN 0 speed slowly cranks up to 6,000 RPM (full throttle). Depending on whether or not I’ve recited the proper black-magic incantations I may-or-may-not be able to turn off one of the two displays and make the fan quickly ramp back down to a normal 2500 RPM. It is interesting to have my external HP monitor button act as though it is wired directly to FAN 0 but that 6,000 RPM fan noise is irritating after about 3.5 seconds.
Apparently there are times when I’ve used the wrong tone or maybe mispronounced an ancient Egyptian God’s name and the simple monitor on/off trick doesn’t work. The system will completely hand and deprive me of the use of my keyboard or mouse after I turn off a monitor; Even after disconnecting all peripherals and opening the laptop to use the track pad on on-board keyboard.
I’ve been using the same hardware, same connections, and same applications for 2 years now (other that a myriad of software upgrades). The only thing that has changed since the “fans working normally” days of last week and the 6,000 RPM mode is having upgraded to OS/X Sierra earlier this week. My guess is someone at Apple buggered a register in the TB I/O code and has overflowed some bits to piss all over other elements of the OS. We’ll see if Sierra *.1 fixes the issue. I can only hope it does.
Looks like my MacBook is at it again – time to sign off… and good luck!
Update: October 19th 2016
What I’ve Learned About The Display Problem
The issue I am having with fan 0 hitting full throttle seems to be related to running both TB ports. For the sake of discussion I am calling the port nearest the power input TB0 and the port closest to the USB input TB1.
The problem appears to triggered by TB0 , but it does require the help of TB1.
Case 1: Reproduction
Plugin HP ZR2440w monitors into TB0 and TB1 using display port.
Make sure TB1 is the primary display.
Start firing up apps. Firefox,Terminal,iMessage,iTunes,Siri,Snagit,Slack in my case then start Photos and the fan quickly ramps up.
Turn off the monitor connected to TB0. The ran immediately starts to ramp down.
Case 2: Add HDMI
Running similar scenarios with the HDMI port pushing video to a third HP ZR2440w seems to have no affect. Whether it is connected or not the results are the same as above when TB0 and TB1 are active. Turn off TB0 and the fans ramp down. Turn on TB0 and the fans ramp back up.
Case 3: Drop TB1
An interesting test case, making TB0 the primary monitor and doing the same exact scenarios above and turning TB1 on/off has no impact on the fan RPM. Once the fan is at 6K RPM it stays that way even though the system clearly shows the TB1 display being dropped from the display stack.
Case 4: TB0 As Primary , Off or Discconnect
This one makes perfect sense when you think about it for a moment; though I do believe OS/X needs to address this as a separate issue. If you make TB0 the primary monitor it will NEVER drop from the display stack. If you turn it off OS/X does not make another display the primary display, keeping the TB0 monitor “in memory”. Same thing if you physically disconnect the TB0 cable. It will NEVER drop.
Because of this turning off or physically disconnecting TB0 while the fan is pegged at 6KRPM has not affect.
If you make TB1 the primary display at this point, OS/X will immediately drop TB0 from the display stack and the fan RPM starts to drop.
Update: October 19th 2016
It Is Siri
Of course it is. The biggest change to OS/X Sierra is the addition of Siri.
Through an errant keyboard click I happened to engage Siri and IMMEDIATELY the fan speed dropped from 6K RPM to a normal 2K RPM. As soon as Siri stopped listening the fan went back to full throttle.
Now that is odd. Repeated tests, same results.
Siri code is toggling SMC registers. Sounds like a buffer overrun to me.
Maybe It’s Not Siri
Turns out that Siri turns off the fans in order to better hear the listener. It seems like Siri is only doing something to force the fan speed to 0 and is not directly related to the issue. An a related note, some gamers have fried their MacBooks because of this by enabling Siri and then getting it stuck that way while running a game. Poof… overheated MacBook. But that’s another issue. No word if the MacBook was completely fried or not but I’m guessing it shut down before that happened.
After the Sierra 10.12.1 patch turning on Siri doesn’t prevent the problem like it had previously. Whenever DP0 + DP1 + HDMI are connected the fan is at 6K RPM. DP0 + DP1 it hovers around 5k RPM. DP0 + HDMI seems better (not great). Turn OFF DP0 and DP1 and the fan almost immediately goes 2K or less RPM.
Maybe Apple support will call me back. It’s been a month with no updates.
Back To El Capitan
Apparently after the initial interest in the problem, Apple decided they couldn’t be bothered with this. Sierra constantly runs the left fan at 5K+ RPM any time the HDMI monitor is attached. I never get a call back from Apple Support when I leave messages these days.
I reverted to El Capitan. Under peak load the left fan is maxing out at less than 4K RPM with all 3 monitors going. Not an apps issue, at least not without “assistance” from macOS Sierra and not a hardware issue.
Apple, you’ve finally failed me on the same level as Microsoft. Boo. I’ll take the 3 hours of downtime in 2 years over countless hours lost to Windows over the same period. Still sucks having gone from 5 minutes of downtime in 2 years to 3 hours and 5 minutes because I had to revert my entire system to a 45-day old backup running El Capitan. That HUGELY SUCKS.
Lesson learned: ignore the future macOS updates from Apple. Since Steve Jobs has gone on to better things Apple has slowly been working its way to mediocrity.