Have just put together a machine I'm hoping will be the start of something powerful enough for VR Development for the next couple of years. It's got a GA-7170N motherboard with a 6700K i7 Processor and a SilentiumPC Fortis 3 HE1425 Cooler.

The problem I'm having at the moment is that the fan will go from being silent to super noisy about 10 times a minute.

Running Prime95 and keeping an eye on the CPU temperature on SpeedFan, the temperature on all 4 cores seems to flick between ~15c to ~60c. The lower value slowly increases whilst Prime95 is running a test. As soon as the test stops running the temperatures rapidly fall (within seconds) back to 15c to 25c.

First thought was that I must have put the heatsink on poorly, took it off, made sure everything was pointing the right way and screwed down tight and the thermal paste was ok. Seems ok.

Next thing I've tried to do as the only real problem here is that I find the constant changing in noise too distracting, was to change the fan speeds using argus hw monitor so that they're always a bit faster. However as temperatures do tend to keep flickering over to showing as 60 degrees + the fans still somewhat erratic and annoying.

Not sure what to try next, benchmarks show that everythings working quite nicely I just can't deal with the constant changing in noise level.