Intel i5 7600K

ASRock Z270M-ITX/AC Motherboard

Corsair Vengeance LPX CMK16GX4M2A2400C16 16GB (2x8GB) DDR4

CPU temperature always reporting either 90 degrees (bios) or 100 degrees (A-Tuning application in Windows).  No variation between the temps reported regardless of CPU load.  Stock Intel and CRYORIG C7 coolers tested - both with 4 pin fan connectors. Neither heatsink gets hot.   Arctic Silver thermal compound and Noctua NT-H1 thermal paste tested, no difference made. 

Tested the available bios revisions for the motherboard: 2.00,1.60, 1.21, 1.10, 1.00 - no difference. 

Reset bios to factory, no difference. 

BIOS has the ability to tune/set the FAN speeds. Despite setting various speeds, no change in fan speed. Tested fans on another motherboard and confirmed fan speeds change correctly.

Both coolers tested on another motherboard (Asus P8Z77-M), fan speeds can be controlled and normal temps by motherboard are reported (45-50 degrees idle, 60-70 full load). 

Used application SpeedFan 4.5.2 and shows 100degrees.

Used application HWiNFO64 v5.50 and shows 34degrees??

Can confirm cpu fan is plugged into the correct header. 

I'd like to see if anyone has any suggestions as to what is going on here, or have any fixes. I'm concerned that the motherboard seems unable to control the cpu fan speed and does not report the correct cpu temp - putting my cpu at risk if it does overheat and the fan does not compensate.

Otherwise it will be RMA time. Not sure I'll get Asrock again.