What case model do you have?
How many FANS connected? And were exactly are they connected?
Do they have 3 pings or 3 pings power connectors?
Fans sizes? For example 120mm or 80mm
Fans Manufacturer and Model number if possible?
Power Supply Used? Exact model number and version?
Thanks for your interest:
case: Lian Li PC-7B PlusII
cpu cooler: Intel boxed for Core i7 860
2 case fans each connected by 4 pin wire (also set in BIOS): Arctic Cooling AF 12025 PWM 120x120x25 mm, 94,7 m^3/h
PSU: Enermax Modu82+ 525W EPS ATX12V 2.3 (speed indicator not connected to mainboard, but that does not matter)
i have the same issue.
its because of the bios update.
its based on whatever algorithm is employed in the intel bios with regards to fan management.
in this board rigorous fan management is disabled. you have the option to enable a basic management technique wherein the bios controls the speed of the fan based on the temperature. In this case the specifics of the plan are not mutable by the user. Or you can just opt to have the fans running at full speed all the time by disabling fan management.
Finally, after nearly 2 years, Intel silently fixed the bug with BIOS 5936. This was the third major and really anoying bug in the BIOS of the DP55WG Board (gigabit LAN disabled, 2x Video Card not found after BIOS updates). Note that there were also two minor ones (keyboard not found and reboot problems after a linuix shutdown).
Seems that the issue was (again!) a software bug in BIOS, and not a failure of the cpu heatsink fan. The support told me to switch it...
I am asking me, if Intel has any quality control for the BIOS releases. This would be very important, as the hardware itself (in high contrast to the BIOS software) is ususally good.