Mario Galaxy FPS drop for no reason (apparently)

[Shonumi]

You probably have a GPU bottleneck. With HLE audio, SMG shouldn't require beastly hardware to enjoyable run it now in recent revisions. The GTX 770 should be able to easily play this game at 4x IR, so it's most likely your GPU running too low like rokclimb15 said. 270 MHz is idling. Make sure you have the maximum performance mode selected in your drivers.