The fan on my motherboard (DP55WG which is essentially the same) only speeds up at 80 degrees so I think what you are finding is normal and as per Intel’s design.
Simple physics means it is easier to transfer the heat away from the CPU when there is a bigger temperature difference between it and the heatsink/ambient air temperature, so the CPU is allowed to reach a high temperature before the fan kicks in full revs, as maintaining it at a lower temperature would require a bigger heatsink and fan, plus there is a limit on how quickly the silicon can dissipate heat to the heat spreader on top it.
Also the diodes measuring the temperature are at the hottest spots in each CPU so overall the CPU is cooler. Also note that Intel's cooling solution is designed to cool a CPU under normal usage, so when using a burn-in program it is possible to cause the CPU to overheat causing it to slow down (thermal throttle).
also as i mentioned in another post.. i know on this board there are several settings in BIOS:
allow fan control [enabled, disabled]
lowest fan speed [off, low]
then for each fan header (3 i think... front, back, and aux) you have the value choices where you have to tell the board if a 3 or 4 pin fan is plugged up to that header... are you sure you have these values set correctly?
if you use the intel desktop control center, then click the fan control, and choose manual control.... and you crank it up.... can you hear them speed up?
are you using latest BIOS?
personally, my case came with only 3-pin fans... i replaced them with 120mm 4-pin/PWM fans... was sure to change the settings in BIOS for them.
I can manually change the speed via the intel desktop control center and they will crank up with no problem... and during video encoding or other high CPU usage times, i can hear them speed up...
In fact, one time I walked in here and the computer sounded a louder than usual. i took a close inspection inside and noticed the back fan was not spinning at all. i barely tapped the fan blade and it kicked off -- i think it is having a problem after resuming from S3... seems like that one fan (that's the only one diff from the others) doesn't want to kick back on after coming out of S3 mode...
Fan control is a balancing act, what one customer likes... another one hates. Can't please everybody.
Most people hate loud fans, so we let the system get a little hotter before we speed up the fans to compensate. If memory serves me right... 70C should not force the fan to speed way up. Here's the key to focus on...
We have red LED's down on the board near the CPU fan port. 2 of them, one for CPU one for CPU-Vreg. If either of them is red... that system is too hot. If your CPU LED never turns on... your CPU is not running too hot for it's design and there's no immediate need to increase fan speed. If that light is on though and fan speed is not going up... there's a problem because when the light is on, the CPU is internally throttling itself back in speed to cool itself off.
Hope that helps.
I just built a new Win 7 Home Premium 64 bit box on a DP55KG motherboard with this same processor. In Desktop Controller, I set the fans to manual control and maxed out the CPU fan at 100%. When I reboot, this change won't happen until I physically open Desktop Controller. I don't want it running all the time, nor do I want to have to remember to open it every time I restart my system. How do I get it to "remember" my settings? Thanks in advance!