I have a GeForce GTX660 and a GTX8800 on my system.
When I had Windows 7 they both were quiet a lot. Now after the upgrade to Windows 8 I notice the following: when system boots up the fans spin fast during the very early initial phase (which sounds correct) but when Windows starts, they slow down to a more quiet speed.
After turning on from standby, the fans spin at maximum speed (and maximum noise). After upgrade from Windows 7 to 8 I reinstalled NVidia drivers just to make sure the system was running them (i.e. Windows 8 setup didn't replace them with its own integrated drivers).
When I had an NVidia-based motherboard, I could change GPU fan speed from NVidia Control Panela after installing NForce driver. Now my motherboard is AMD-based but SLI-compliant (it's a Sabertooth 990FX by ASUS, based on AMD 990 chipset).
How can I tell the GPU fans to stay quiet unless I'm playing a 3D game?