Good find, I'll try this out right now since I just updated to 10.12.6. I'll try the 10.12.6 Kexts first and see what happens (they are also v1.5.1 so I imagine they will be the same as the 10.12.5 Kexts). Unfortunately my iStat trial expired so I'm having to find other ways to monitor statistics.
I did a new test with all the AMD kexts in version 1.5.1 (mac OS combo Update 10.12.5).
I was able to decrease by 2 degrees Celsius. Now the Sierra 10.12.5 stands at 34 degrees Celsius in idle (only open Terminal, Active Monitor, Istat Menu and gfxcardstatus).
The kexts 1.5.1 installed on the hard disk require more dependency (AMDLegacyFramebuffer.kext, AMDLegacySupport.kext) than the kexts of the pendrive installer. This difference is relative to the construction of kext.
I tried manually loading the kets of AMDLegacySupport.kext and AMDLegacyFramebuffer.kext to satisfy the dependency of the AMD6000Controller.kext, but it did not reduce the temperature so much.
So I put these kexts for automatic loading and lowered the temperature to 34 degrees Celsius.
Remembering that the AMDRadeonX3000.kext is the crucial kext to drastically lower the temperature.
I use FGuarani's method to move the kexts.
You have to watch the Active Monitor tab Energy, the Spotlight is consuming resources and increasing the temperature.
On my first boot after moving the kexts and loads them, I waited 10 minutes until the Spotlight reduce energy consumption.
The temperature in idle was 38 degrees Celsius after finishing high consumption of Spotlight (30%).
Now comes the interesting, on the second day, and in the second boot, the temperature has dropped even more. I also noticed that in the Istat Menu GPU Die Analog, the temperature dropped rapidly after loading the AMDRadeonX3000.kext.
My Spotlight is with all the options unchecked.
System Preferences -> Spotlight -> Search Results
AMDRadeonX3000.kext is manually loaded to prevent screen freeze during boot (IOConsoleUsers IOScreenLockState).
load automatic - kexts 1.5.1 - /System/Library/Extensions
AMD6000Controller.kext
AMDFramebuffer.kext
AMDLegacyFramebuffer.kext
AMDLegacySupport.kext
AMDSupport.kext
load manual - kext 1.5.1 - /kexts-1.5.1-combo-update
cd /kexts-1.5.1-combo-update
sudo kextload AMDRadeonX3000.kext
kextstat | grep AMD
com.apple.kext.AMDLegacySupport (1.5.1)
com.apple.kext.AMD6000Controller (1.5.1)
com.apple.kext.AMDLegacyFramebuffer (1.5.1)
com.apple.AMDRadeonX3000 (1.5.1)
Download macOS Sierra 10.12.5 Combo Update
https://support.apple.com/kb/DL1918?locale=en_US
Update:
The AMDRadeonX3000.kext that is manually loaded is outside the user directory ( /Users ).
Use the TAB key to autocomplete the names of partitions and files.
1 - mac OS Sierra -> Applications -> Utilities -> Terminal
cd /
sudo mkdir kexts-1.5.1-combo-update
2 - Install mac OS Sierra 10.12.5 combo update
3 - After reboot, the system rebuild cache,
Probably the system will hang on IOSetLockState IOConsoleUsers.
I had done the Safe Mode procedure (press Shift at boot), but I noticed that after rebuild caching, it doubled the memory consumption. As I had described in an earlier post.
So, boot normal (without any key press at boot).
So I let the screen freeze on IOConsoleUsers IOScreenLockState (system hangs because AMDRadeonX3000.kext is in /System/Library/Extensions after install mac os sierra 10.12.5 combo update).
Press the Power button to turn off and exit the frozen screen.
Press the Power button again to turn on the Macbook Pro and now enter the Recovery Mode (Command + R) and move the kexts. Method of FGuarani.
4 - Recovery Mode (Command + R) - Utilities -> Terminal -> Move all AMD and ATI kexts to /kexts-1.5.1-combo-update .
My Sierra 10.12.5 installed hard disk on partition name MacSierra
mv -v /Volumes/MacSierra/System/Library/Extensions/AMD*.* /Volumes/MacSierra/kexts-1.5.1-combo-update
mv -v /Volumes/MacSierra/System/Library/Extensions/ATI*.* /Volumes/MacSierra/kexts-1.5.1-combo-update
5 - Move these kexts back to the /System/Library/Extensions (Sierra installed on hard disk)
AMD6000Controller.kext
AMDFramebuffer.kext
AMDLegacyFramebuffer.kext
AMDLegacySupport.kext
AMDSupport.kext
mv -v /Volumes/MacSierra/kexts-1.5.1-combo-update/AMD6000Controller.kext /Volumes/MacSierra/System/Library/Extensions/
mv -v /Volumes/MacSierra/kexts-1.5.1-combo-update/AMDFramebuffer.kext /Volumes/MacSierra/System/Library/Extensions/
mv -v /Volumes/MacSierra/kexts-1.5.1-combo-update/AMDLegacyFramebuffer.kext /Volumes/MacSierra/System/Library/Extensions/
mv -v /Volumes/MacSierra/kexts-1.5.1-combo-update/AMDLegacySupport.kext /Volumes/MacSierra/System/Library/Extensions/
mv -v /Volumes/MacSierra/kexts-1.5.1-combo-update/AMDSupport.kext /Volumes/MacSierra/System/Library/Extensions/
6 - Go back to the /
cd /
7 - Restart the system. Leave Recovery Mode -> enter normal boot
reboot
8 - After login -> manual load AMDRadeonX3000.kext
cd /kexts-1.5.1-combo-update
sudo kextload AMDRadeonX3000.kext