AMD 7850, fans making a jolt every 60 seconds after ZeroCore kicks in

Hi, I'm using this card http://www.msi.com/product/vga/R7850-Power-Edition-2GD5... and recently noticed that when ZeroCore is activated, the fans stop, but every 1 minute they would spin violently for a second (sounds like when they are making the "dust out" routine).
MSI Afterburner clearly shows this behavior in the hardware monitor screen.

This guy is having the same problem http://hardforum.com/showpost.php?s=1c7655088aeb5720d55...

Is this normal? Thanx