The readings are right, i have a lot of S9's and i loaded 650 FF FW and the temps went crazy.. some showed 82 temp but in the firmware it said display upto 82 only so god only knows what the temps were.. for that extra 1.5TH it aint worth burning your boards..
Just my opinion.. tried and tested.. i have auto freq on all of mine.. loading the 650 FF FW is for very cold climates
82°C-95°C I think just fine for Antminer devices.. Don't be afraid like that,this devices can handling with max. 125 °C.so I wrote to Bitmain and they said me this.