I swapped heat-sinks. The temperature didn't follow it.
I tested with smaller amount of thermal paste. That is how it looked after the last time:
After this, I tried to apply pressure evenly during installing heat-sink to avoid missed corner.
Temperature went down to 78C on hottest core. Still too high. BTW I think I was running Prime95 for too long and so the system halted.
Like I mentioned earlier, setting fans to the full speed (I have AN-0126L4 with 7000 rpm) bring temperature down to another 4C.
I'm thinking to get a more powerful fans (noise is not a concern anymore), for example this
11000 RPM fan that is compatible with the case.
I think replacing 4 fans that sit across CPUs should do the trick and bring the temperature down to about 72C. Which should be acceptable.
Makes sense?
PS: I also could get a new mother board for testing. But only if it is really necessary....