It seems CPU A is too hot with native fan profile. The Mac should keep it at or below 85C, I assume that 89 is not the max, but just the momentary temperature during you capture the screen. It may actually go slightly over 90C.
20C separation between CPU diode and heat sink means the thermal paste is working, but can be a little bit better (e.g. around 15C).
A simple work around would be setup your own Boost A fan profile in MacsFanControl. e.g.
View attachment 650366
You can try some different numbers and make it run at or below 80C. No need to be too extreme, and just make a profile that you are happy with (in both temperature and fan noise)
The way to find out the Min / Max temperatures is simple.
e.g. You want to keep it at 70C as you first pic does.
Assume CPU A idle at 50C - 800RPM, Max at 70C - 4000 RPM.
4000 - 800 = 3200
e.g. If you want the fan start spin up at 60C.
70 - 60 = 10
That means you want the fan spin up 320 RPM for every 1C
Boost A max RPM is 5200.
5200 - 800 = 4400
4400 / 320 ~ 14
So, the profile will be
Min 60C
Max 74C (60+14)
In this case, the fan will start spinning up from 60C, increase 320 RPM for every 1C, and slowly reach your decided equilibrium point (70C, 4000RPM).
